Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 598,686	$ 484,336
Accumulated Amortization	(335,507)	(297,313)
Intangible Assets, Net	$ 263,179	187,023
Remaining Weighted Average Amortization Period in Years	9 years 1 month 6 days
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 327,334	244,329
Accumulated Amortization	(137,333)	(110,640)
Intangible Assets, Net	$ 190,001	133,689
Remaining Weighted Average Amortization Period in Years	7 years 3 months 24 days
Backlog
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 136,266	133,592
Accumulated Amortization	(135,847)	(132,441)
Intangible Assets, Net	$ 419	1,151
Remaining Weighted Average Amortization Period in Years	1 year 1 month 3 days
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 74,797	54,723
Accumulated Amortization	(17,057)	(12,855)
Intangible Assets, Net	$ 57,740	41,868
Remaining Weighted Average Amortization Period in Years	16 years 2 months 12 days
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 37,760	29,212
Accumulated Amortization	(27,659)	(25,546)
Intangible Assets, Net	$ 10,101	3,666
Remaining Weighted Average Amortization Period in Years	3 years 10 months 24 days
Patented rights and developed technology
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 22,529	22,480
Accumulated Amortization	(17,611)	(15,831)
Intangible Assets, Net	$ 4,918	$ 6,649
Remaining Weighted Average Amortization Period in Years	3 years 4 months 24 days