Non-Qualified Retirement, Savings And Investment Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Number of non-qualified retirement savings and investment plans	2
Basis points	300
Deferred Compensation Liability, Current and Noncurrent		$ 17,600,000
Investments, employee benefit plans, at fair value	11,678,000	23,365,000
Common stock held by non-qualified plan		900,000
Executive Deferred Compensation Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Deferred Compensation Liability, Current and Noncurrent	17,200,000	17,600,000
Investments, employee benefit plans, at fair value	14,200,000	13,600,000
Trading Securities, Realized Gain (Loss)	(100,000)	1,400,000	3,700,000
General and Administrative Expense [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Compensation expense	800,000	900,000	1,100,000
Non-Qualified Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Deferred Compensation Liability, Current and Noncurrent	10,400,000	10,600,000
Increase (Decrease) in Deferred Compensation	(500,000)	800,000	1,900,000
Investments, employee benefit plans, at fair value	9,500,000	9,700,000
Trading Securities, Realized Gain (Loss)	500,000	700,000	1,900,000
Common stock held by non-qualified plan	$ 900,000