Earnings Per Common 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
Net income per share calculations for basic and diluted methods
Net income available to common stockholders	$ 30,829	$ 24,828	$ 71,999	$ 74,382
Shares:
Weighted average common shares outstanding	54,586	55,410	54,579	54,783
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)	152	236	217	275
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation	54,738	55,646	54,796	55,058
Basic earnings per common share (in dollars per share)	$ 0.56	$ 0.45	$ 1.32	$ 1.36
Diluted earnings per common share (in dollars per share)	$ 0.56	$ 0.45	$ 1.31	$ 1.35
Common Stock
Shares:
Number of anti-dilutive securities (in shares)	300	237	300	385