Equity Incentive Compensation Plans (Range of Exercise Prices) (Details) (USD $) In Thousands, except Share data, unless otherwise specified									12 Months Ended
	Dec. 31, 2011 year		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2008		Dec. 31, 2011 $7.00-$15.00 year	Dec. 31, 2011 $15.01-$25.00 year	Dec. 31, 2011 $25.01-$35.00 year	Dec. 31, 2011 $35.01-$48.50 year
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices, Lower Range Limit (in dollars)									$ 7.00	$ 15.01	$ 25.01	$ 35.01
Range of Exercise Prices, Upper Range Limit (in dollars)									$ 15.00	$ 25.00	$ 35.00	$ 48.50
Stock Options Outstanding, Number of Options	1,520,690								199,000	287,000	655,001	379,689
Stock Options Outstanding, Weighted Average Remaining Contractual Life (Years)	4.47								2.13	2.90	4.51	6.79
Stock Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 30.32		$ 25.87		$ 25.36		$ 25.16		$ 12.36	$ 21.60	$ 31.65	$ 44.01
Stock Options Outstanding, Aggregate Intrinsic Value (in dollars)	$ 17,798	[1]	$ 35,974	[1]	$ 15,296	[1]	$ 0	[1]	$ 5,902	$ 5,861	$ 6,792	$ 0
Stock Options Exercisable, Number of Options	1,434,020								199,000	287,000	655,001	293,019
Stock Options Exercisable, Weighted Average Remaining Contractual Life (Years)	4.18								2.13	2.90	4.51	6.09
Stock Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 29.22								$ 12.36	$ 21.60	$ 31.65	$ 42.68
Stock Options Exercisable, Aggregate Intrinsic Value (in dollars)	$ 18,360								$ 5,902	$ 5,861	$ 6,792	$ 0

[1] The intrinsic value of a stock option is the amount by which the market value of the underlying stock at the end of the related period exceeds the exercise price of the option.