Earnings Per Share (Details)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation between basic and diluted earnings per share
Weighted average number of common shares outstanding	32,000,000	32,000,000	31,700,000	31,500,000	32,000,000	31,600,000	31,700,000	31,200,000	30,800,000
Dilutive impact of stock based compensation	298,002		499,683		305,042	487,247
Weighted average number of common and common equivalent shares outstanding for the period	32,300,000	32,300,000	32,200,000	32,000,000	32,300,000	32,100,000	32,100,000	31,500,000	31,000,000
Number of common shares outstanding at the end of the period	31,920,554		31,645,359		31,920,554	31,645,359
Weighted average anti-dilutive shares excluded from the computation of diluted earnings per share	701,099		230,665		646,046	175,614