Non-Qualified Retirement, Savings And Investment Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	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
Investments, employee benefit plans, at fair value	$ 12,755,000	$ 11,678,000
Executive Deferred Compensation Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Basis points				300
Deferred Compensation Liability, Current and Noncurrent	11,700,000	17,200,000
Assets Held-in-trust, Current	3,500,000
Investments, employee benefit plans, at fair value	6,000,000	14,200,000
Trading Securities, Realized Gain (Loss)	(1,200,000)	100,000	(1,400,000)
General and Administrative Expense [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Compensation expense	800,000	800,000	900,000
Non-Qualified Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Deferred Compensation Liability, Current and Noncurrent	11,200,000	10,400,000
Increase (Decrease) in Deferred Compensation	700,000	(500,000)	800,000
Investments, employee benefit plans, at fair value	10,200,000	9,500,000
Trading Securities, Realized Gain (Loss)	(800,000)	500,000	(700,000)
Common stock held by non-qualified plan	$ 1,000,000	$ 900,000