Earnings per 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 earnings per common share
Net income									$ 39,961	$ 11,639	$ 6,012
Less income allocated to participating securities									609	179	69
Net income attributable to common shareholders	13,031	10,762	14,593	1,575	8,531	603	5,909	(3,404)	39,352	11,460	5,943
Weighted average common shares outstanding									22,168,500	22,029,374	21,894,569
Basic income per common share (in dollars per share)	$ 0.58	$ 0.48	$ 0.65	$ 0.07	$ 0.38	$ 0.03	$ 0.26	$ (0.15)	$ 1.78	$ 0.52	$ 0.27
Earnings per common share assuming dilution
Net income									39,961	11,639	6,012
Less income allocated to participating securities									609	179	69
Net income attributable to common shareholders	$ 13,031	$ 10,762	$ 14,593	$ 1,575	$ 8,531	$ 603	$ 5,909	$ (3,404)	$ 39,352	$ 11,460	$ 5,943
Weighted average common shares outstanding									22,168,500	22,029,374	21,894,569
Incremental shares applicable to stock based compensation									20,346	37,800	69,742
Weighted average common shares assuming dilution									22,188,846	22,067,174	21,964,311
Earnings per common share assuming dilution (in dollars per share)	$ 0.58	$ 0.47	$ 0.64	$ 0.07	$ 0.38	$ 0.02	$ 0.26	$ (0.15)	$ 1.77	$ 0.51	$ 0.26