Segment Information - Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total sales	$ 932,253	$ 723,601	$ 1,848,287	$ 1,495,632
Specialty Products & Electronics
Segment Reporting Information [Line Items]
Total sales	324,798	339,188	639,863	717,457
Transit Products
Segment Reporting Information [Line Items]
Total sales	253,764	49,643	512,182	98,438
Brake Products
Segment Reporting Information [Line Items]
Total sales	192,557	141,979	373,016	293,885
Remanufacturing, Overhaul & Build
Segment Reporting Information [Line Items]
Total sales	126,556	156,981	255,616	315,014
Other
Segment Reporting Information [Line Items]
Total sales	$ 34,578	$ 35,810	$ 67,610	$ 70,838