Goodwill and Acquired Intangible Assets Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 21,547,000	$ 20,962,000	$ 17,070,000
Future amortization expense, 2014	20,600,000
Future amortization expense, 2015	18,900,000
Future amortization expense, 2016	14,500,000
Future amortization expense, 2017	10,200,000
Future amortization expense, 2018	$ 4,400,000