Non-Qualified Retirement, Savings And Investment Plans (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Number of non-qualified retirement savings and investment plans	2		2
Investments, employee benefit plans, at fair value	$ 22,017,000		$ 22,017,000		$ 23,365,000
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	16,800,000		16,800,000		17,600,000
Investments, employee benefit plans, at fair value	13,100,000		13,100,000		13,600,000
Trading Securities, Realized Gain (Loss)	1,400,000	(800,000)	900,000	(600,000)
General and Administrative Expense [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Compensation expense	16,778	300,000	500,000	700,000
Non-Qualified Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Deferred Compensation Liability, Current and Noncurrent	9,600,000		9,600,000		10,600,000
Increase (Decrease) in Deferred Compensation	(1,300,000)	800,000	1,100,000	500,000
Investments, employee benefit plans, at fair value	9,000,000		9,000,000		9,700,000
Trading Securities, Realized Gain (Loss)	1,200,000	(700,000)	900,000	(500,000)
Common stock held by non-qualified plan	$ 700,000		$ 700,000		$ 900,000