Share-based Compensation (Nonvested Options) (Details) (Nonvested Option Shares [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Nonvested Option Shares [Member]
Nonvested Awards, Number of Shares [Roll Forward]
Nonvested awards, Shares, beginning balance	180,005	247,690	303,900
Nonvested options, Granted	45,000	45,000	45,000
Nonvested options, Vested	(90,005)	(112,685)	(101,210)
Nonvested options, Canceled	0	0	0
Nonvested awards, Shares, ending balance	135,000	180,005	247,690
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Exercise Price [Roll Forward]
Nonvested options, Weighted Average Exercise Price, beginning balance (in dollars per share)	$ 17.17	$ 14.07	$ 11.79
Nonvested options, Granted, Weighted Average Exercise Price (in dollars per share)	$ 16.94	$ 20.58	$ 21.70
Nonvested options, Vested, Weighted Average Exercise Price (in dollars per share)	$ 14.60	$ 11.71	$ 10.61
Nonvested options, Canceled, Weighted Average Exercise Price (in dollars per share)	$ 0.00	$ 0.00	$ 0.00
Nonvested options, Weighted Average Exercise Price, ending balance (in dollars per share)	$ 18.80	$ 17.17	$ 14.07