Share-Based Arrangements Stock Options Activity (Details) (Stock Options [Member], USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at December 31, 2010	985,079
Granted	183,815
Exercised	(178,472)
Forfeited or expired	(10,764)
Outstanding at December 31, 2011	979,658	985,079
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding at December 31, 2010, Weighted average-exercise price	$ 23.35	$ 20.81
Granted, Weighted Average Grant Date Fair Value	$ 31.78
Exercised, Weighted average-exercise price	$ 18.25
Forfeited or expired, Weighted average exercise price	$ 19.61
Options outstanding at December 31, 2011, Weighted average-exercise price	$ 23.35	$ 20.81
Weighted-average remaining contractual term - options outstanding	6.6
Aggregate intrinsic value - options outstanding (in thousands)	$ 4,703,000
Options exercisable	391,969
Weighted-average remaining contractual term - options exercisable	4.8
Aggregate intrinsic value - options exercisable (in thousands)	2,875,000
Weighted-average exercise price - options exercisable	$ 19.98
Intrinsic Value	$ 2,900,000	$ 1,500,000	$ 300,000
Expected option term	6.5	6.5	6.5
Expected volatility	43.90%	46.10%	47.70%
Risk-free interest rate	2.90%	3.20%	2.00%
Expected dividend yield	2.20%	3.30%	2.20%
Per share fair value of options granted	$ 12.05	$ 9.28	$ 6.43