Net Income Per Share (Details)	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
Earnings Per Share [Abstract]
Common shares									21,739,300	23,180,633	24,850,830
Vested restricted stock units									517,804	670,156	558,825
Basic number of weighted average shares outstanding	21,109,349	21,888,591	22,653,393	23,463,380	23,438,153	23,672,635	23,974,099	24,330,027	22,257,104	23,850,789	25,409,655
Dilutive effect of stock options									3,293	31,180	48,005
Dilutive effect of restricted stock and restricted stock units									71,004	127,624	141,296
Weighted average shares outstanding: Diluted	21,171,235	21,895,222	22,658,891	23,528,466	23,575,786	23,708,043	24,017,273	24,426,127	22,331,401	24,009,593	25,598,956
Restricted stock outstanding excluded from calculation of diluted net income per share									0	0	0