Stock-Based Compensation (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Components of stock-based compensation expense
Total stock-based compensation	[1]	$ 12,171	$ 10,458	$ 35,313	$ 31,155
Stock options [Member]
Components of stock-based compensation expense
Total stock-based compensation		735	947	2,590	3,000
Restricted stock awards and units [Member]
Components of stock-based compensation expense
Total stock-based compensation		7,786	6,571	22,474	18,312
Performance-based restricted stock units [Member]
Components of stock-based compensation expense
Total stock-based compensation		2,414	2,264	7,116	7,133
Employee stock purchase plan [Member]
Components of stock-based compensation expense
Total stock-based compensation		$ 1,236	$ 676	$ 3,133	$ 2,710

[1] Total stock-based compensation is presented in this table on a gross basis, consistent with the additional paid-in capital impact recorded in stockholders' equity. On the Company's consolidated statements of operations and consolidated statements of cash flows, stock-based compensation is presented net of foreign exchange impact and capitalization of eligible software development-related costs.