Net Income Per Share (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income Per Share [Abstract]
Common shares									23,180,633	24,850,830	25,890,521
Vested restricted stock units									670,156	558,825	411,768
Basic number of weighted average shares outstanding	23,438,153	23,672,635	23,974,099	24,330,027	24,756,286	24,908,247	25,925,627	26,157,672	23,850,789	25,409,655	26,302,289
Dilutive effect of stock options									31,180	48,005	102,651
Dilutive effect of restricted stock and restricted stock units									127,624	141,296	195,915
Dilutive number of weighted average shares outstanding	23,575,786	23,708,043	24,017,273	24,426,127	24,926,004	24,962,054	25,979,872	26,283,801	24,009,593	25,598,956	26,600,855
Restricted stock outstanding excluded from calculation of diluted net income per share									0	0	0