Business Combinations - Estimates of Acquired Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 4,708	$ 972	$ 3,241
Weighted Average Estimated Useful Life (yrs)	14 years	10 years	10 years
Trademarks and Trade Names [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	1,799	338	2,067
Weighted Average Estimated Useful Life (yrs)	15 years	15 years	9 years
Non-competition Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 604	$ 22	$ 205
Weighted Average Estimated Useful Life (yrs)	5 years	5 years	3 years