Stock Compensation Plans and Share-Based Compensation Awards - RSU (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock Compensation Plans and Share-Based Compensation Awards
Share-based compensation expense	$ 5,890	$ 2,977	$ 9,475	$ 4,822
RSUs
Stock Compensation Plans and Share-Based Compensation Awards
Share-based compensation expense	2,400	1,400	4,100	2,100
Unrecognized compensation expense	$ 25,100	$ 17,400	$ 25,100	$ 17,400
Vesting period			4 years
Weighted average period outstanding for unvested RSUs			2 years 9 months 18 days	3 years 3 months 18 days
Total fair value of share based awards vested			$ 5,200	$ 2,100
Number outstanding
Balance at beginning of period (in shares)			876
Granted (in shares)			610
Vested (in shares)			(242)
Forfeited (in shares)			(27)
Balance at end of period (in shares)	1,217		1,217
Weighted average grant date fair value
Balance at beginning of period (in dollars per share)			$ 22.30
Granted (in dollars per share)			23.19
Vested (in dollars per share)			21.48
Forfeited (in dollars per share)			22.29
Balance at end of period (in dollars per share)	$ 22.91		$ 22.91