Earnings Per Share - Computation of basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Computation of basic and diluted earnings per share
Net income	$ 47,607	$ 48,362	$ 104,587	$ 136,709
Preferred Stock Dividends, Income Statement Impact	(1,814)	0	(1,814)	0
Dividends and undistributed earnings allocated to unvested shares	(356)	(351)	(779)	(982)
Net income available to common shareholders	$ 45,437	$ 48,011	$ 101,994	$ 135,727
Weighted average shares outstanding:
Basic (in shares)	87,129	79,663	81,815	79,714
Effect of dilutive securities
Diluted (in shares)	87,205	79,667	81,876	79,718
Net income per common share:
Basic (in dollars per share)	$ 0.52	$ 0.60	$ 1.25	$ 1.70
Diluted (in dollars per share)	$ 0.52	$ 0.60	$ 1.25	$ 1.70
Stock options
Effect of dilutive securities
Dilutive securities (in shares)	0	1	0	1
Restricted stock units
Effect of dilutive securities
Dilutive securities (in shares)	76	3	61	3