Goodwill and Acquired Intangible Assets - Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 6,848,000	$ 6,060,000
Future amortization expense to be recognized in remainder of 2014	25,200,000
Future amortization expense 2015	26,800,000
Future amortization expense 2016	25,200,000
Future amortization expense 2017	23,100,000
Future amortization expense 2018	$ 16,200,000