Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income available to common stockholders	$ 18,531	$ 11,508	$ 19,663	$ 10,710
Weighted average common shares outstanding, basic (in shares)	48,020,000	47,972,000	48,002,000	47,938,000
Dilutive SARs (treasury method) (in shares)	0	0	0	5,000
Weighed average common shares outstanding, dilutive (in shares)	48,020,000	47,972,000	48,002,000	47,943,000
Earnings per share - basic (in dollars per share)	$ 0.39	$ 0.24	$ 0.41	$ 0.22
Earnings per share - diluted (in dollars per share)	$ 0.39	$ 0.24	$ 0.41	$ 0.22
Net Income Per Share Calculations
Dilutive SARs (treasury method) (in shares)	0	0	0	5,000
Stock Appreciation Rights (SARs)
Earnings Per Share [Abstract]
Dilutive SARs (treasury method) (in shares)			0	0
Net Income Per Share Calculations
Dilutive SARs (treasury method) (in shares)			0	0