Share-Based Payments - Schedule of Stock-Based Compensation Expense by Award Type Included Within the Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 18,588	$ 24,193	$ 55,243	$ 55,170
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	11,552	12,953	37,065	38,736
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,917	3,338	14,708	7,940
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	350	246	1,070	838
Other stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,769	$ 7,656	$ 2,400	$ 7,656