Goodwill and Purchased Intangible Assets - Summary of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 77,038	$ 68,299
Accumulated Amortization	(50,737)	(40,791)
Net Book Value	26,301	27,508	24,068
Customer Lists and Customer Relationships
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	47,179	45,569
Accumulated Amortization	(29,449)	(24,520)
Net Book Value	17,730	21,049
Non-Compete Agreements
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	12,087	12,168
Accumulated Amortization	(11,555)	(10,513)
Net Book Value	532	1,655
Intellectual Property
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,730	5,765
Accumulated Amortization	(2,608)	(1,879)
Net Book Value	3,122	3,886
Tradename
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,752	4,797
Accumulated Amortization	(5,404)	(3,879)
Net Book Value	1,348	918
Backlog
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,290	0
Accumulated Amortization	(1,721)	0
Net Book Value	$ 3,569	$ 0