Acquisitions - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Detail) - Acquisitions [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($)
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 8,327
Weighted Average Amortization Period at Acquisition Date in Years	6 years 9 months 18 days
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 4,814
Weighted Average Amortization Period at Acquisition Date in Years	3 years 3 months 18 days
Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 822
Weighted Average Amortization Period at Acquisition Date in Years	3 years 1 month 6 days
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 2,448
Weighted Average Amortization Period at Acquisition Date in Years	15 years
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 243
Weighted Average Amortization Period at Acquisition Date in Years	5 years