Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 2,499	$ 1,931	$ 7,256	$ 5,530
Cost of revenue
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	2,113	1,498	6,034	4,221
Sales and marketing
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	293	323	939	924
Technology and development
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	4	5	14	14
General and administrative
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 89	$ 105	$ 269	$ 371