Goodwill and Acquired Intangible Assets - Narrative (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 8,403,000	$ 4,859,000	$ 23,654,000	$ 16,653,000
Future amortization expense to be recognized in remainder of 2014	8,400,000		8,400,000
Future amortization expense 2015	26,800,000		26,800,000
Future amortization expense 2016	25,200,000		25,200,000
Future amortization expense 2017	23,100,000		23,100,000
Future amortization expense 2018	$ 16,200,000		$ 16,200,000