Summary of Financial Information by Reportable Segment and Product Line (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013 Segment	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012	Aug. 31, 2012
Segment Reporting Information [Line Items]
Number of reportable segments	4
Net sales	$ 370,370	$ 378,024	$ 747,618	$ 770,823
Operating profit (Loss)	41,944	49,456	93,246	106,737
Assets	2,023,831		2,023,831		2,007,119
Industrial
Segment Reporting Information [Line Items]
Net sales	98,999	98,342	200,121	198,595
Operating profit (Loss)	26,350	26,691	53,356	54,624
Assets	272,791		272,791		268,735
Energy
Segment Reporting Information [Line Items]
Net sales	80,794	78,937	171,563	159,358
Operating profit (Loss)	9,677	11,632	25,064	24,849
Assets	534,279		534,279		540,409
Electrical
Segment Reporting Information [Line Items]
Net sales	69,902	77,105	139,341	159,938
Operating profit (Loss)	5,072	5,801	12,900	10,778
Assets	443,474		443,474		437,914
Engineered Solutions
Segment Reporting Information [Line Items]
Net sales	120,675	123,640	236,593	252,932
Operating profit (Loss)	8,275	13,281	15,900	32,280
Assets	672,836		672,836		667,550
Vehicle Systems
Segment Reporting Information [Line Items]
Net sales	59,675	68,916	120,862	145,280
Other
Segment Reporting Information [Line Items]
Net sales	61,000	54,724	115,731	107,652
General Corporate
Segment Reporting Information [Line Items]
Operating profit (Loss)	(7,430)	(7,949)	(13,974)	(15,794)
Assets	$ 100,451		$ 100,451		$ 92,511