Share-Based Compensation (Schedule of Outstanding Stock Options) (Details) (USD $)	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Options outstanding, December 31,	509,422	384,507	253,836	159,668
Weighted Average Exercise Price, December 31, Outstanding	$ 42.03	$ 33.24	$ 27.72	$ 29.03
Contractual Life, Weighted Average, Outstanding	4.69
Grant Date 05-16-07 [Member]
Options outstanding, December 31,	15,000
Weighted Average Exercise Price, December 31, Outstanding	$ 34.25
Contractual Life, Weighted Average, Outstanding	0.010
Grant Date 02-04-08 [Member]
Options outstanding, December 31,	7,750
Weighted Average Exercise Price, December 31, Outstanding	$ 29.24
Contractual Life, Weighted Average, Outstanding	0.020
Grant Date 04-29-08 [Member]
Options outstanding, December 31,	15,000
Weighted Average Exercise Price, December 31, Outstanding	$ 30.30
Contractual Life, Weighted Average, Outstanding	0.040
Grant Date 02-25-09 [Member]
Options outstanding, December 31,	15,000
Weighted Average Exercise Price, December 31, Outstanding	$ 25.29
Contractual Life, Weighted Average, Outstanding	0.030
Grant Date 02-25-10 [Member]
Options outstanding, December 31,	15,000
Weighted Average Exercise Price, December 31, Outstanding	$ 35.99
Contractual Life, Weighted Average, Outstanding	0.090
Grant Date 03-02-10 [Member]
Options outstanding, December 31,	48,338
Weighted Average Exercise Price, December 31, Outstanding	$ 34.48
Contractual Life, Weighted Average, Outstanding	0.780
Grant Date 03-19-10 [Member]
Options outstanding, December 31,	50,000
Weighted Average Exercise Price, December 31, Outstanding	$ 37.33
Contractual Life, Weighted Average, Outstanding	0.810
Grant Date 05-28-10 [Member]
Options outstanding, December 31,	13,334
Weighted Average Exercise Price, December 31, Outstanding	$ 41.18
Contractual Life, Weighted Average, Outstanding	0.220
Grant Date 02-22-11 [Member]
Options outstanding, December 31,	60,000
Weighted Average Exercise Price, December 31, Outstanding	$ 45.58
Contractual Life, Weighted Average, Outstanding	0.490
Grant Date 02-25-11 [Member]
Options outstanding, December 31,	270,000
Weighted Average Exercise Price, December 31, Outstanding	$ 46.22
Contractual Life, Weighted Average, Outstanding	2.200