Business Combinations - Estimates of Acquired Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 28,501	$ 3,067
Weighted Average Estimated Useful Life (yrs)	8 years	8 years
Trademarks and Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 15,496	$ 1,535
Weighted Average Estimated Useful Life (yrs)	15 years	15 years
Covenants Not-to-compete [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 1,607	$ 434
Weighted Average Estimated Useful Life (yrs)	5 years	5 years
Backlog [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 13,400
Weighted Average Estimated Useful Life (yrs)	1 year 6 months