Capitalized Software (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Impaired Intangible Assets [Line Items]
Capitalized internal-use software development costs	$ 164,669		$ 164,669		$ 146,261
Less: Accumulated amortization	(112,759)		(112,759)		(99,625)
Capitalized software, net	51,910		51,910		$ 46,636
Amortization expense	4,331	$ 4,798	13,265	$ 14,708
Cost of revenue [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	4,175	4,625	12,774	14,224
Sales and marketing [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	59	51	163	117
General and administrative [Member]
Impaired Intangible Assets [Line Items]
Amortization expense	$ 97	$ 122	$ 328	$ 367