Stockholders' Equity - Summary of Components of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 7,863	$ 4,302	$ 20,287	$ 13,229
Cost of services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	449	334	1,286	910
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	1,238	761	3,385	2,235
Technology and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	2,514	867	6,226	3,766
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 3,662	$ 2,340	$ 9,390	$ 6,318