Shareholders' Equity (Details) (USD $)
 0 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended 0 Months Ended 1 Months Ended 0 Months Ended 3 Months Ended 0 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended 12 Months Ended 9 Months Ended
Dec. 28, 2012
Apr. 30, 2013
Apr. 30, 2012
Apr. 30, 2013
Apr. 30, 2012
Jul. 31, 2012
Aug. 31, 2010
Jan. 04, 2012
Walsh [Member]
Apr. 22, 2013
Walsh [Member]
Jan. 28, 2013
Walsh [Member]
Dec. 17, 2012
Walsh [Member]
Apr. 23, 2012
Walsh [Member]
Oct. 24, 2011
Walsh [Member]
Dec. 14, 2011
Ecology and Environment do Brasil LTDA [Member]
Nov. 18, 2011
Walsh Peru [Member]
Dec. 28, 2012
Gustavson [Member]
Mar. 13, 2013
Lowham Walsh [Member]
Oct. 31, 2012
Lowham Walsh [Member]
Jul. 31, 2011
Gustavson [Member]
Apr. 30, 2013
Gustavson [Member]
Jul. 31, 2012
Gustavson [Member]
Apr. 30, 2013
Walsh 01 [Member]
Apr. 30, 2013
Walsh 02 [Member]
Jul. 31, 2012
Ecology and Environment do Brasil LTDA [Member]
Apr. 30, 2013
Walsh 03 [Member]
Apr. 30, 2013
Lowham 01 [Member]
Apr. 30, 2013
Lowham 02 [Member]
Jul. 31, 2012
Walsh Peru [Member]
May 01, 2012
Gestion Ambiental Consultores [Member]
Jul. 31, 2012
Gestion Ambiental Consultores [Member]
Jul. 31, 2012
Walsh 04 [Member]
Jul. 31, 2012
Walsh 05 [Member]
Jul. 31, 2012
Walsh 06 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Gustavson [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Gustavson [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 01 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 01 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 02 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 02 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Ecology and Environment do Brasil LTDA [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Ecology and Environment do Brasil LTDA [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 03 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 03 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Lowham 01 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Lowham 01 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Lowham 02 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Lowham 02 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh Peru [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh Peru [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Gestion Ambiental Consultores [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Gestion Ambiental Consultores [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 04 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 04 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 05 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 05 [Member]
Apr. 30, 2013
Noncontrolling Interest [Member]
Walsh 06 [Member]
Jul. 31, 2012
Noncontrolling Interest [Member]
Walsh 06 [Member]
Apr. 30, 2013
Class A [Member]
Class A and Class B common stock [Abstract]                                                                                                                        
Percentage equity holders entitled to elect Board of Directors (in hundredths)                                                                                                                       25.00%
Minimum percentage of the number of outstanding Class A shares to combined classes of shares (in hundredths)                                                                                                                       10.00%
Voting power of Class A common share holders to the Class B common share holders (in hundredths)                                                                                                                       10.00%
Dividends, Cash [Abstract]                                                                                                                        
Cash dividends declared   $ 0 $ 0 $ 1,018,540 $ 1,017,776 $ 2,000,000                                                       $ 0 $ 0                                                  
Accrued dividends payable   1,018,783 1,028,881 1,018,783 1,028,881 1,000,000                                                                                                            
Stock Repurchase [Abstract]                                                                                                                        
Number of shares authorized to be repurchased (in shares)             200,000                                                                                                          
Remaining number of shares authorized to be repurchased (in shares)   93,173   93,173                                                                                                                
Schedule of Equity Method Investments [Line Items]                                                                                                                        
Issuance of shares to noncontrolling interests                                                                   0 41,634 0 [1] 41,634 [1]                                              
Transfers from noncontrolling interests                                                                   (775,935) (619,775) (293,102) [2] 0 [2] (18,316) [3] 0 [3] (243,653) [4] 0 [4] 0 [5] 77,539 [5] (182,125) [6] 0 [6] (8,737) [7] 0 [7] (30,002) [8] 0 [8] 0 [9] (238,677) [9] 0 [10] (7,452) [10] 0 [11] (97,634) [11] 0 [12] (277,514) [12] 0 (76,037)  
Net transfers from noncontrolling interests       (775,935)   (578,141)                                                                                                            
Shares issued (in shares)                                         600                                                                              
Shares repurchased (in shares)                                       2,800   50 495 5,389 370 25 75 26,482   25 166 496 152                                                      
Interest purchased (in hundredths)                                     1.50%                                                                                  
Interest Acquired (in hundredths)               1.30% 0.10% 1.30% 0.90% 0.40% 0.40% 4.00% 3.90% 6.70%                                                                                        
Purchase of noncontrolling interest       $ 595,556 $ 892,294     $ 300,000 $ 100,000 $ 200,000 $ 200,000 $ 100,000 $ 100,000 $ 200,000 $ 400,000 $ 400,000 $ 100,000 $ 100,000                     $ (100,000)                                                              
Percentage of acquisition paid in cash (in hundredths)               67.00%   67.00%           50.00%                                                                                        
Percentage of acquisition paid with stock (in hundredths)               33.00%   33.00%                                                                                                    
Term of note issued 3 years                                                                                                                      
Interest repurchased (in hundredths)                                                         2.50%                                                              
[1] On August 1, 2011 the noncontrolling shareholders of Gustavson Associates, LLC ("Gustavson"), a subsidiary of Walsh Environmental Scientists and Engineers, LLC ("Walsh") purchased an additional 1.5% of newly issued shares of the company for less than $0.1 million in cash.
[2] On December 28, 2012, Gustavson purchased an additional 6.7% of its shares from noncontrolling shareholders for $0.4 million. Half of the purchase price was paid in cash and Gustavson issued a three year note for the other half.
[3] On April 22, 2013 the Company purchased an additional 0.1% of Walsh from noncontrolling shareholders for less than $0.1 million in cash.
[4] On January 28, 2013 the Company purchased an additional 1.3% of Walsh from noncontrolling shareholders for $0.2 million. Two thirds of the purchase price was paid in cash while the remaining one third was paid for with E&E stock.
[5] On December 14, 2011, the Company purchased an additional 4.0% of Ecology and Environment do Brasil LTDA (E&E Brasil) from noncontrolling shareholders for $0.2 million cash.
[6] On December 17, 2012 the Company purchased an additional 0.9% of Walsh from noncontrolling shareholders for $0.2 million in cash.
[7] On March 13, 2013 Lowham-Walsh Engineering & Environment Services LLC ("Lowham"), a subsidiary of Walsh, purchased shares from noncontrolling shareholders for less than $0.1 million in cash.
[8] During the three months ending October 31, 2012, Lowham purchased shares from noncontrolling shareholders for less than $0.1 million in cash.
[9] On November 18, 2011, Walsh Peru S.A. Ingenieros y Cientificos Consultores ("Walsh Peru"), a subsidiary of Walsh, purchased an additional 3.9% of its shares from noncontrolling shareholders for $0.4 million in cash.
[10] On May 1, 2012 Gestion Ambiental Consultores S.A ("GAC"), a subsidiary of the Company, purchased 2.5% of its stock back from noncontrolling shareholders for less than $0.1 million in cash.
[11] On April 23, 2012 the Company purchased an additional 0.4% of Walsh from noncontrolling shareholders for $0.1 million in cash.
[12] On January 4, 2012, the Company purchased an additional 1.3% of Walsh from noncontrolling shareholders for $0.3 million. Two thirds of the purchase price was paid in cash while the remaining one third was paid for with E&E stock.