Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income per share calculations for basic and diluted methods
Net income									$ 102,953	$ 98,928	$ 62,726
Shares:
Weighted average common shares outstanding									54,852,000	48,854,000	42,685,000
Dilutive effect of outstanding options, warrants and restricted stock units as determined by the application of the treasury stock method (in shares)									280,000	361,000	441,000
Weighted average common shares outstanding, as adjusted for diluted earnings per share calculation									55,132,000	49,215,000	43,126,000
Basic earnings per common share (in dollars per share)	$ 0.52	$ 0.45	$ 0.43	$ 0.48	$ 0.52	$ 0.55	$ 0.51	$ 0.45	$ 1.88	$ 2.02	$ 1.47
Diluted earnings per common share (in dollars per share)	$ 0.52	$ 0.45	$ 0.43	$ 0.48	$ 0.51	$ 0.55	$ 0.51	$ 0.45	$ 1.87	$ 2.01	$ 1.45
Warrants
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)									191,278	191,278
Restricted stock unit
Anti-dilutive securities excluded from the calculation of common stock equivalents
Number of anti-dilutive securities (in shares)									201,029	172,571