Capitalized Software (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Impaired Intangible Assets [Line Items]
Capitalized internal-use software development costs	$ 158,938		$ 158,938		$ 146,261
Less: Accumulated amortization	(108,428)		(108,428)		(99,625)
Capitalized software, net	50,510		50,510		$ 46,636
Amortization expense	4,453	$ 4,956	8,934	$ 9,910
Cost of revenue [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	4,284	4,801	8,599	9,599
Sales and marketing [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	59	33	104	66
General and administrative [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	$ 110	$ 122	$ 231	$ 245