Intangible Assets - Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Customer relationships, Gross Carrying Amount	$ 57,157	$ 57,319
Non-compete agreements, Gross Carrying Amount	12,238	12,077
Indefinite-lived intangible assets:
Gross Carrying Amount	167,292	160,803
Accumulated Amortization	(91,481)	(84,119)
Net Balance	75,811	76,684
Trademarks [Member]
Indefinite-lived intangible assets:
Net Balance, Indefinite-Lived Intangible Assets	38,172	35,801
Net Balance, Indefinite-Lived Intangible Assets	38,172	35,801
Domain Names [Member]
Indefinite-lived intangible assets:
Net Balance, Indefinite-Lived Intangible Assets	4,400	4,400
Net Balance, Indefinite-Lived Intangible Assets	4,400	4,400
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Weighted-Average Amortization Period (Years)	10 years
Net Balance, Finite-Lived Intangible Assets	10,735	14,837
Indefinite-lived intangible assets:
Accumulated Amortization	(46,422)	(42,482)
Acquired Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Weighted-Average Amortization Period (Years)	12 years
Net Balance, Finite-Lived Intangible Assets	22,138	21,472
Acquired technology, Gross Carrying Amount	55,325	51,206
Indefinite-lived intangible assets:
Accumulated Amortization	(33,187)	(29,734)
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, Weighted-Average Amortization Period (Years)	4 years
Net Balance, Finite-Lived Intangible Assets	366	174
Indefinite-lived intangible assets:
Accumulated Amortization	$ (11,872)	$ (11,903)