Non-Qualified Retirement, Savings And Investment Plans (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2009	Dec. 31, 2011
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	$ 12,221,000		$ 12,221,000			$ 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	15,900,000		15,900,000			17,200,000
Investments, employee benefit plans, at fair value	7,400,000		7,400,000			14,200,000
Assets Held-in-trust, Current	5,200,000		5,200,000
Trading Securities, Realized Gain (Loss)	24,000	(48,000)	1,100,000	500,000
Common stock held by non-qualified plan	100,000		100,000
General and Administrative Expense [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Compensation expense	100,000	200,000	500,000	500,000
Non-Qualified Plan [Member]
Schedule of Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits
Deferred Compensation Liability, Current and Noncurrent	10,900,000		10,900,000			10,400,000
Investments, employee benefit plans, at fair value	10,000,000		10,000,000			9,500,000
Trading Securities, Realized Gain (Loss)	300,000	9,000	(600,000)	(300,000)
Increase (Decrease) in Deferred Compensation	(300,000)	(100,000)	600,000	200,000
Common stock held by non-qualified plan	$ 900,000		$ 900,000			$ 900,000