Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net income per share calculations for basic and diluted methods
Net income available to common stockholders	$ 24,862	$ 16,479	$ 46,779	$ 31,649
Shares:
Weighted average common shares outstanding	48,815,000	38,311,000	48,796,000	38,302,000
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)	409,000	441,000	407,000	444,000
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation	49,224,000	38,752,000	49,203,000	38,746,000
Basic earnings per common share (in dollars per share)	$ 0.51	$ 0.43	$ 0.96	$ 0.83
Diluted earnings per common share (in dollars per share)	$ 0.51	$ 0.43	$ 0.95	$ 0.82
Stock options
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)				10,850
RSU
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)				128,622
Warrants
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)			191,278	191,278