Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic and Diluted Earnings per Share [Line Items]
Net income		$ 3,114	$ 15,018	$ 25,541	$ 38,697
Weighted-average common shares outstanding (in shares)		25,366,283	25,023,753	25,288,086	25,007,204
Weighted-average common shares for EPS calculation (in shares)		25,795,476	25,287,630	25,629,577	25,132,339
Basic earnings per common share (in dollars per share)		$ 0.12	$ 0.60	$ 1.01	$ 1.55
Diluted earnings per common share (in dollars per share)		$ 0.12	$ 0.59	$ 1.00	$ 1.54
Awards excluded from diluted earnings per share calculation (in shares)	[1]	0	431,599	0	443,596
Restricted Stock Unit Awards [Member]
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding (in shares)		155,270	125,135	155,270	125,135
Stock Options [Member]
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding (in shares)		273,923	138,742	186,221	0

[1] Outstanding awards that are not "in-the-money" are excluded from the diluted earnings per share calculation because the effect of including them would have been anti-dilutive.