Stock-Based Compensation (Stock Appreciation Rights Award Activity) (Details) (Stock Appreciation Rights (SARs) [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Appreciation Rights (SARs) [Member]
SARs Activity [Roll Forward]
Outstanding, Beginning	160,168	111,048	78,512
Granted	72,509	63,024	36,255
Exercised	(37,834)	(7,685)	(3,719)
Forfeited	0	(6,219)	0
Outstanding, Ending	194,843	160,168	111,048
SARs, Weighted Average Exercise Price [Roll Forward]
Oustanding, Beginning (in usd per share)	$ 40.34	$ 39.74	$ 38.04
Granted (in usd per share)	$ 42.44	$ 41.13	$ 42.68
Exercised (in usd per share)	$ 37.81	$ 39.15	$ 32.50
Forfeited (in usd per share)	$ 0.00	$ 39.18	$ 0.00
Oustanding, Ending (in usd per share)	$ 41.61	$ 40.34	$ 39.74
SARs, Additional Disclosures
Exercisable	55,146	58,900	41,439
Exercisable (in usd per share)	$ 41.40	$ 39.72	$ 39.16