Segment Information - Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total sales	$ 957,931	$ 675,574	$ 2,806,218	$ 2,171,206
Specialty Products & Electronics
Segment Reporting Information [Line Items]
Total sales	335,143	334,349	975,006	1,051,806
Transit Products
Segment Reporting Information [Line Items]
Total sales	276,913	44,996	789,096	143,434
Brake Products
Segment Reporting Information [Line Items]
Total sales	177,165	134,900	550,181	428,785
Remanufacturing, Overhaul & Build
Segment Reporting Information [Line Items]
Total sales	132,018	129,264	387,634	444,278
Other
Segment Reporting Information [Line Items]
Total sales	$ 36,692	$ 32,065	$ 104,301	$ 102,903