EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic and Diluted Earnings per Share [Line Items]
Net income	$ 11,995	$ 12,368	$ 3,114	$ 22,427	$ 30,895	$ 19,534	$ 15,018	$ 23,679	$ 49,904	$ 89,126	$ 59,137
Weighted-average common shares outstanding (in shares)									25,335,706	25,047,405	25,230,854
Weighted-average common shares, Diluted (in shares)									25,804,678	25,235,996	25,493,663
Basic earnings per common share (in usd per share)	$ 0.47	$ 0.49	$ 0.12	$ 0.89	$ 1.23	$ 0.78	$ 0.60	$ 0.95	$ 1.97	$ 3.56	$ 2.34
Diluted earnings per common share (in usd per share)	$ 0.46	$ 0.48	$ 0.12	$ 0.88	$ 1.21	$ 0.77	$ 0.59	$ 0.94	$ 1.93	$ 3.53	$ 2.32
Awards excluded from diluted calculation (in shares)									0	343,390	835,610
Restricted Stock Awards
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of restricted stock awards (in shares)									155,059	122,840	114,313
Stock Options
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of restricted stock awards (in shares)									313,913	65,751	148,496