Segment Information - Sales by Product (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Total sales	$ 2,236,284	$ 1,111,680	$ 3,829,901	$ 2,167,857
Remanufacturing, Overhaul & Build
Segment Reporting Information [Line Items]
Total sales	1,171,147	127,202	1,753,324	262,900
Specialty Products & Electronics
Segment Reporting Information [Line Items]
Total sales	443,333	434,399	861,447	820,947
Transit Products
Segment Reporting Information [Line Items]
Total sales	310,839	282,130	605,656	556,409
Brake Products
Segment Reporting Information [Line Items]
Total sales	254,260	217,574	496,482	433,192
Other
Segment Reporting Information [Line Items]
Total sales	$ 56,705	$ 50,375	$ 112,992	$ 94,409