Stock-Based Compensation - Options Valuation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-Based Compensation
Total stock-based compensation expense (in dollars)	$ 7,137	$ 6,852
Stock options
Stock-Based Compensation
Total stock-based compensation expense (in dollars)	$ 2,507	$ 2,674
Valuation assumptions:
Expected volatility (as a percent)	56.10%	69.70%
Expected term (years)	5 years 3 months	6 years 7 days
Risk-free interest rate (as a percent)	1.22%	2.50%
Weighted average grant-date fair value (in dollars per share)	$ 33.78	$ 34.98