Acquisitions - Summary of Preliminary Estimated Fair Values of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Apr. 05, 2017	Mar. 14, 2017	Dec. 31, 2016	Dec. 14, 2016	Nov. 17, 2016	Aug. 01, 2016	May 05, 2016
Business Acquisition [Line Items]
Goodwill	$ 2,384,758			$ 2,078,765
TTC
Business Acquisition [Line Items]
Current assets		$ 3,746
Property, plant & equipment		5,909
Goodwill		16,309
Other intangible assets		12,300
Other assets		0
Total assets acquired		38,264
Total liabilities assumed		(5,753)
Net assets acquired		$ 32,511
ATP
Business Acquisition [Line Items]
Current assets			$ 11,666
Property, plant & equipment			5,354
Goodwill			31,934
Other intangible assets			22,100
Other assets			0
Total assets acquired			71,054
Total liabilities assumed			(5,800)
Net assets acquired			$ 65,254
Workhorse
Business Acquisition [Line Items]
Current assets					$ 9,137
Property, plant & equipment					0
Goodwill					24,373
Other intangible assets					19,400
Other assets					0
Total assets acquired					52,910
Total liabilities assumed					(9,083)
Net assets acquired					$ 43,827
Precision Turbo
Business Acquisition [Line Items]
Current assets						$ 4,145
Property, plant & equipment						1,346
Goodwill						4,019
Other intangible assets						5,200
Other assets						0
Total assets acquired						14,710
Total liabilities assumed						(884)
Net assets acquired						$ 13,826
Gerken
Business Acquisition [Line Items]
Current assets							$ 32,706
Property, plant & equipment							7,667
Goodwill							17,470
Other intangible assets							30,560
Other assets							1,706
Total assets acquired							90,109
Total liabilities assumed							(27,262)
Net assets acquired							$ 62,847
Unitrac
Business Acquisition [Line Items]
Current assets								$ 11,476
Property, plant & equipment								1,768
Goodwill								2,442
Other intangible assets								1,230
Other assets								0
Total assets acquired								16,916
Total liabilities assumed								(2,145)
Net assets acquired								$ 14,771