Earnings Per Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 13,603	$ 20,628	$ 25,546	$ 34,813	$ 64,461
Less: earnings attributable to unvested shares	(32)	(43)	(46)	(73)
Net income available to participating common shareholders	$ 13,571	$ 20,585	$ 25,500	$ 34,740
Basic number of common shares, outstanding	20,435,846	21,876,265	20,807,777	21,870,343
Dilutive effect of stock equivalents	287,094	375,151	302,026	373,421
Dilutived number of weighted average common shares outstanding	20,722,940	22,251,416	21,109,803	22,243,764
Earnings per common share - Basic	$ 0.66	$ 0.94	$ 1.23	$ 1.59
Earnings per common share - Diluted	$ 0.65	$ 0.93	$ 1.21	$ 1.56
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	391,069	383,971	376,137	385,701