Share-Based Compensation (Summary of Stock Option Activity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Shares - Beginning balance		397,914	337,812
Shares, Granted	2,700	205,489	238,050
Shares, Forfeited		3,284	7,869
Shares - Ending balance	398,284	416,477	398,284
Stock Options [Member]
Shares - Beginning balance		1,071,454
Shares, Granted		205,489
Shares, Exercised		(5,481)
Shares, Expired unexercised		(1,500)
Shares, Forfeited		(3,284)
Shares - Ending balance		1,266,678
Shares, Vested or expected to vest at June, 2011		1,235,424
Shares, Exercisable at June 30, 2011		850,201
Weighted Average Exercise Price, Outstanding at January 1, 2011		$ 36.27
Weighted Average Exercise Price, Granted		$ 36.51
Weighted Average Exercise Price, Exercised		$ 28.64
Weighted Average Exercise Price, Expired unexercised		$ 53.63
Weighted Average Exercise Price, Outstanding at June 30, 2011		$ 36.33
Weighted Average Exercise Price, Forfeited		$ 31.45
Weighted Average Exercise Price, Vested or expected to vest at June, 2011		$ 36.33
Weighted Average Exercise Price, Exercisable at June 30, 2011		$ 38.35
Weighted Average Remaining Contractual Term (Years), Outstanding at June 30, 2011		6.66
Weighted Average Remaining Contractual Term (Years), Vested or expected to vest at June, 2011		6.61
Weighted Average Remaining Contractual Term (Years), Exercisable at June 30, 2011		5.52
Aggregate Intrinsic Value, Outstanding at June 30, 2011		$ 10,178
Aggregate Intrinsic Value, Vested or expected to vest at June, 2011		9,949
Aggregate Intrinsic Value, Exercisable at June 30, 2011		$ 6,668