Stock-Based Compensation Stock-Based Compensation (Activity Pertaining to Nonemployee Director Stock Award Plan) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Ending Balance	614,133
Directors Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Director option awards		3,500
Number of Shares, Beginning Balance	199,500	178,500	143,496
Weighted Average Grant Date Price, Beginning Balance	$ 48.37	$ 48.77	$ 49.38
Number of Shares, Granted	0	31,500	52,504	437
Weighted Average Grant Date Price, Granted	$ 0.00	$ 53.81	$ 37.62
Number of Shares, Exercised	(7,000)	(10,500)	(3,500)
Weighted Average Grant Date Price, Exercised	$ 17.54	$ 21.96	$ 20.28
Number of Shares, Forfeited	0	0	(14,000)
Weighted Average Grant Date Price, Forfeited	$ 0.00	$ 0.00	$ 58.20
Number of Shares, Ending Balance	192,500	199,500	178,500	143,496
Weighted Average Grant Date Price, Ending Balance	$ 49.39	$ 48.37	$ 48.77	$ 49.38