Stock-Based Compensation (Schedule of Performance Unit Awards) (Details) (Performance Shares [Member], USD $)	3 Months Ended	6 Months Ended
	Mar. 31, 2012	Jun. 30, 2012 Incentive Plan, 2010-2012 [Member]	Jun. 30, 2012 Incentive Plan, 2011-2013 [Member]	Jun. 30, 2012 Incentive Plan, 2012-2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date		March 2, 2010	March 15, 2011	March 6, 2012
Units		36,541	34,002	43,042
Grant Date Fair Value	$ 38.46	$ 31.83	$ 38.46	$ 27.49
Aggregate Fair Value		$ 1,163,100	$ 1,307,717	$ 1,183,225
Vesting Date		March 2, 2013	March 15, 2014	March 6, 2015