Stock-Based Compensation 4 (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Outstanding	1,663,340	1,783,956	1,493,131	1,200,552
Granted	4,276	376,795	417,647
Exercised	(77,477)	(47,322)	(50,174)
Forfeited	(47,415)	(38,648)	(74,894)
Weighted-average exercise price - Outstanding	$ 20.63	$ 20.50	$ 19.18	$ 18.02
Weighted-average exercise price - Granted	$ 28.10	$ 24.67	$ 21.64
Weighted-average exercise price - Exercised	$ 15.33	$ 12.64	$ 12.55
Weighted-average exercise price - Forfeited	$ 25.33	$ 19.93	$ 18.82
Exercisable	1,278,950	900,965	494,775
Weighted-average exercise price - Exercisable	$ 19.71	$ 20.53	$ 22.06