Share-Based Compensation - Unrecognized Share-Based Compensation Expense (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 82,015
Stock option
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 11,994
Average Expected Recognition Period - in Years	2 years 8 months 27 days
Restricted stock units
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 70,021
Average Expected Recognition Period - in Years	2 years 8 months 5 days