EARNINGS PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Basic and Diluted Earnings per Share [Line Items]
Net income	$ 34,796	$ 325	$ 10,685	$ 13,331	$ 26,526	$ 11,725	$ 15,496	$ 22,393	$ 59,137		$ 76,140		$ 40,212
Weighted-average common shares outstanding									25,230,854		25,325,695		25,447,918
Weighted-average common shares, Diluted									25,493,663		25,531,375		25,504,526
Basic earnings per common share (in usd per share)	$ 1.39	$ 0.01	$ 0.42	$ 0.53	$ 1.04	$ 0.46	$ 0.61	$ 0.89	$ 2.34	[1]	$ 3.01	[1]	$ 1.58
Diluted earnings per common share (in usd per share)	$ 1.38	$ 0.01	$ 0.42	$ 0.52	$ 1.04	$ 0.45	$ 0.61	$ 0.88	$ 2.32	[1]	$ 2.98	[1]	$ 1.58
Awards excluded from diluted calculation									835,610	[2]	638,478	[2]	901,008	[2]
Restricted Stock Awards [Member]
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding									114,313		59,849		54,338
Stock Options [Member]
Basic and Diluted Earnings per Share [Line Items]
Add dilutive effect of share-based awards outstanding									148,496		145,831		2,270

[1] The sum of the quarterly reported amounts may not equal the full year, as each is computed independently.

[2] 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.