Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income per share calculations for basic and diluted methods
Net income available to common stockholders	$ 25,806	$ 24,085	$ 41,170	$ 49,554
Shares:
Weighted average common shares outstanding	54,489,000	55,638,000	54,576,000	54,464,000
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)	216,000	303,000	231,000	300,000
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation	54,705,000	55,941,000	54,807,000	54,764,000
Basic earnings per common share (in dollars per share)	$ 0.47	$ 0.43	$ 0.75	$ 0.91
Diluted earnings per common share (in dollars per share)	$ 0.47	$ 0.43	$ 0.75	$ 0.90
Stock options
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			39,525	48,107
Restricted stock unit
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			367,121	169,258
Warrants
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			191,278	191,278