Net Income Per Common Share - Basic and Diluted Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic
Net income applicable to common stock	$ 20,130	$ 2,008	$ 46,625	$ 45,110	$ 22,138	$ 91,735
Average common shares outstanding (shares)	56,165,452		58,461,024		56,350,134	58,523,007
Net income per common share - basic (usd per share)	$ 0.36		$ 0.80		$ 0.39	$ 1.57
Diluted
Net income applicable to common stock	$ 20,130	$ 2,008	$ 46,625	$ 45,110	$ 22,138	$ 91,735
Average common shares outstanding (shares)	56,165,452		58,461,024		56,350,134	58,523,007
Effect of dilutive stock-based compensation (shares)	160,024		157,952		164,465	146,049
Average common shares outstanding - diluted (shares)	56,325,476		58,618,976		56,514,599	58,669,056
Net income per common share - diluted (usd per share)	$ 0.36		$ 0.80		$ 0.39	$ 1.56