Stock-based Awards - Stock Compensation Costs (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock based Compensation Cost
Total stock-based compensation expense	$ 7,395	$ 2,043	$ 11,540	$ 3,616
Amount capitalized to internal software use	321	145	614	251
Total stock-based compensation cost	7,716	2,188	12,154	3,867
Cost of revenue
Stock based Compensation Cost
Total stock-based compensation expense	113	28	163	53
Sales and marketing
Stock based Compensation Cost
Total stock-based compensation expense	1,307	580	2,344	1,104
Technology and development
Stock based Compensation Cost
Total stock-based compensation expense	1,156	443	1,865	783
General and administrative
Stock based Compensation Cost
Total stock-based compensation expense	$ 4,819	$ 992	$ 7,168	$ 1,676