Acquisitions - Pro Forma Operating Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Jul. 31, 2015		Apr. 30, 2015		Jan. 31, 2015		Oct. 31, 2014		Jul. 31, 2014		Apr. 30, 2014		Jan. 31, 2014		Oct. 31, 2013		Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Business Acquisition [Line Items]
Net sales	$ 288,636		$ 290,227		$ 282,628		$ 310,240		$ 316,733		$ 309,577		$ 291,194		$ 307,530		$ 1,171,731	$ 1,225,034	$ 1,157,792
(Loss) earnings from continuing operations, as reported	$ (39,394)		$ 17,213		$ 11,584		$ 15,499		$ (96,981)		$ 20,183		$ 10,517		$ 18,135		4,902	(48,146)	(138,257)
Nonvoting Common Stock [Member]
Business Acquisition [Line Items]
(Loss) earnings from continuing operations, as reported																	$ 4,902	$ (48,238)	$ (138,495)
Basic (loss) earnings from continuing operations per Class A Common Share, as reported	$ (0.77)	[1]	$ 0.34	[1]	$ 0.23	[1]	$ 0.30	[1]	$ (1.89)	[1]	$ 0.39	[1]	$ 0.20	[1]	$ 0.35	[1]	$ 0.10	$ (0.93)	$ (2.70)
Diluted (loss) earnings from continuing operations per Class A Common Share, as reported	$ (0.77)	[1]	$ 0.33	[1]	$ 0.23	[1]	$ 0.30	[1]	$ (1.89)	[1]	$ 0.39	[1]	$ 0.20	[1]	$ 0.35	[1]	$ 0.10	$ (0.93)	$ (2.70)
Precision Dynamics Corporation [Member]
Business Acquisition [Line Items]
Net sales																		$ 1,157,792
Net sales, pro forma																		1,226,217
(Loss) earnings from continuing operations, as reported																		(138,257)
(Loss) earnings from continuing operations, pro forma																		$ (133,957)
Precision Dynamics Corporation [Member] | Nonvoting Common Stock [Member]
Business Acquisition [Line Items]
Basic (loss) earnings from continuing operations per Class A Common Share, as reported																		$ (2.70)
Basic (loss) earnings from continuing operations per Class A Common Share, pro forma																		(2.61)
Diluted (loss) earnings from continuing operations per Class A Common Share, as reported																		(2.70)
Diluted (loss) earnings from continuing operations per Class A Common Share, pro forma																		$ (2.61)

[1] *** The sum of the quarters does not equal the year-to-date total for fiscal 2015 and fiscal 2014 due to the quarterly changes inweighted-average shares outstanding.