Stock Compensation Plans and Share-Based Compensation Awards - RSU (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock Compensation Plans and Share-Based Compensation Awards
Share-based compensation expense	$ 3,019	$ 1,758	$ 7,841	$ 53,893
RSUs
Stock Compensation Plans and Share-Based Compensation Awards
Share-based compensation expense	1,300	$ 600	3,400	$ 800
Unrecognized compensation expense	$ 16,100		$ 16,100
Vesting period			4 years
Weighted average period outstanding for unvested RSUs			3 years
Number outstanding
Balance at beginning of period (in shares)			506
Granted (in shares)			515
Vested (in shares)			(139)
Forfeited (in shares)			(36)
Balance at end of period (in shares)	846		846
Weighted average grant date fair value
Balance at beginning of period (in dollars per share)			$ 16.30
Granted (in dollars per share)			26.21
Vested (in dollars per share)			16.27
Forfeited (in dollars per share)			21.79
Balance at end of period (in dollars per share)	$ 22.11		$ 22.11