Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income per share calculations for basic and diluted methods
Net income available to common stockholders	$ 24,828	$ 26,859	$ 74,382	$ 73,638
Shares:
Weighted average common shares outstanding	55,410,000	48,892,000	54,783,000	48,828,000
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)	236,000	355,000	275,000	388,000
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation	55,646,000	49,247,000	55,058,000	49,216,000
Basic earnings per common share (in dollars per share)	$ 0.45	$ 0.55	$ 1.36	$ 1.51
Diluted earnings per common share (in dollars per share)	$ 0.45	$ 0.55	$ 1.35	$ 1.50
RSU
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			385,322	172,571
Warrants
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			191,278	191,278