Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income per share calculations for basic and diluted methods
Net income available to common stockholders	$ 26,859	$ 18,784	$ 73,638	$ 50,433
Shares:
Weighted average common shares outstanding	48,892,000	45,324,000	48,828,000	40,669,000
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)	355,000	440,000	388,000	400,000
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation	49,247,000	45,764,000	49,216,000	41,069,000
Basic earnings per common share (in dollars per share)	$ 0.55	$ 0.41	$ 1.51	$ 1.24
Diluted earnings per common share (in dollars per share)	$ 0.55	$ 0.41	$ 1.50	$ 1.23
Stock options
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)				78,540
RSU
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			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