SCHEDULE 13G

Amendment No. 5 
Eagle Materials Incorporated 
Common Stock 
Cusip #26969P108 


Cusip #26969P108 
Item 1:	Reporting Person - FMR Corp.
Item 4:	Delaware
Item 5:	43,357 
Item 6:	0 
Item 7:	1,277,583 
Item 8:	0 
Item 9:	1,277,583 
Item 11:	13.427% 
Item 12:	    HC


Cusip #26969P108  
Item 1:	Reporting Person - Edward C. Johnson 3d 
Item 4:	United States of America
Item 5:	0 
Item 6:	0 
Item 7:	1,277,583 
Item 8:	0 
Item 9:	1,277,583 
Item 11:	13.427% 
Item 12:	IN 




	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)




Item 1(a).	Name of Issuer:	

		Eagle Materials Incorporated 

Item 1(b).	Name of Issuer's Principal Executive Offices:

		2728 N. Harwood  
		Dallas, TX  75201
		  

Item 2(a).	Name of Person Filing: 

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None, 
Residence:

		82 Devonshire Street, Boston, 
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock 

Item 2(e).	CUSIP Number:  

		26969P108 

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) 
and the person filing, FMR Corp., is a parent holding company 
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See 
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	1,277,583 

	(b)	Percent of Class:	13.427% 

	(c)	Number of shares as to which such 
person has:  

	(i)	sole power to vote or to direct 
the vote:	43,357 

	(ii)	shared power to vote or to 
direct the vote:	0 

	(iii)	sole power to dispose or to 
direct the disposition of:	1,277,583 

	(iv)	shared power to dispose or to 
direct the disposition of:	0 



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another 
Person.

	Various persons have the right to receive or the power to 
direct the receipt of dividends from, or the proceeds from the 
sale of, the Common Stock of Eagle Materials Incorporated.  
The interest of one person, Fidelity Contrafund, an investment 
company registered under the Investment Company Act of 
1940, in the Common Stock of Eagle Materials Incorporated, 
amounted to 589,700 shares or 6.198% of the total outstanding 
Common Stock at September 30, 2005. 

Item 7.	Identification and Classification of the Subsidiary Which 
Acquired the Security Being Reported on By the Parent 
Holding Company.

	See attached Exhibit A. 

Item 8.	Identification and Classification of Members of 
the Group.

	Not applicable.  See attached Exhibit A. 

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge 
and belief, the securities referred to above were acquired in the 
ordinary course of business and were not acquired for the 
purpose of and do not have the effect of changing or 
influencing the control of the issuer of such securities and 
were not acquired in connection with or as a participant in any 
transaction having such purpose or effect.

Signature

	After reasonable inquiry and to the best of my knowledge and 
belief, I certify that the information set forth in this statement 
is true, complete and correct. 

October 11, 2005 			
Date

/s/Eric D. Roiter			
Signature

Eric D, Roiter			
Duly authorized under Power of Attorney
dated December 30, 1997 by and on behalf of FMR Corp. and 
its direct and indirect subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule 13G, 
Fidelity Management & Research Company ("Fidelity"), 82 
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR Corp. and an investment adviser 
registered under Section 203 of the Investment Advisers Act 
of 1940, is the beneficial owner of 1,234,226 shares or 
12.971% of the Common Stock outstanding of Eagle Materials 
Incorporated  ("the Company") as a result of acting as 
investment adviser to various investment companies registered 
under Section 8 of the Investment Company Act of 1940.

	The ownership of one investment company, Fidelity 
Contrafund, amounted to 589,700 shares or 6.198% of the 
Common Stock outstanding. Fidelity Contrafund has its 
principal business office at 82 Devonshire Street, Boston, 
Massachusetts 02109.

	Edward C. Johnson 3d and FMR Corp., through its 
control of Fidelity, and the funds each has sole power to 
dispose of the 1,234,226 shares owned by the Funds.

	Members of the family of Edward C. Johnson 3d, 
Chairman of FMR Corp., are the predominant owners, directly 
or through trusts, of Series B shares of common stock of FMR 
Corp., representing 49% of the voting power of FMR Corp.  
The Johnson family group and all other Series B shareholders 
have entered into a shareholders' voting agreement under 
which all Series B shares will be voted in accordance with the 
majority vote of Series B shares.  Accordingly, through their 
ownership of voting common stock and the execution of the 
shareholders' voting agreement, members of the Johnson 
family may be deemed, under the Investment Company Act of 
1940, to form a controlling group with respect to FMR Corp.

	Neither FMR Corp. nor Edward C. Johnson 3d, 
Chairman of FMR Corp., has the sole power to vote or direct 
the voting of the shares owned directly by the Fidelity Funds, 
which power resides with the Funds' Boards of Trustees.  
Fidelity carries out the voting of the shares under written 
guidelines established by the Funds' Boards of Trustees.

	Fidelity Management Trust Company, 82 Devonshire 
Street, Boston, Massachusetts 02109, a wholly-owned 
subsidiary of FMR Corp. and a bank as defined in Section 
3(a)(6) of the Securities Exchange Act of 1934, is the 
beneficial owner of  42,257 shares or 0.444% of the Common 
Stock outstanding of the Company as a result of its serving as 
investment manager of the institutional account(s).

	Edward C. Johnson 3d and FMR Corp., through its 
control of Fidelity Management Trust Company, each has sole 
dispositive power over 42,257 shares and sole power to vote 
or to direct the voting of 42,257 shares of Common Stock 
owned by the institutional account(s) as reported above.

	Strategic Advisers, Inc., 82 Devonshire Street, Boston, 
MA 02109, a wholly-owned subsidiary of FMR Corp. and an 
investment adviser registered under Section 203 of the 
Investment Advisers Act of 1940, provides investment 
advisory services to individuals.  As such, FMR Corp.'s 
beneficial ownership includes 1,100 shares, or 0.012%, of the 
Common Stock stock outstanding of Eagle Materials 
Incorporated, beneficially owned through Strategic Advisers, 
Inc.



	SCHEDULE 13G - TO BE INCLUDED IN 
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on October 11, 2005, agree 
and consent to the joint filing on their behalf of this Schedule 
13G in connection with their beneficial ownership of the 
Common Stock of Eagle Materials Incorporated at September 
30, 2005.

	FMR Corp.

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Duly authorized under Power of Attorney dated 
December 30, 1997, by and on behalf of FMR Corp. and its 
direct and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Duly authorized under Power of Attorney dated 
December 30, 1997, by and on behalf of Edward C. Johnson 
3d

	Fidelity Management & Research Company

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Senior V.P. and General Counsel

	Fidelity Contrafund

	By /s/ Eric D. Roiter			
	Eric D. Roiter
	Secretary