Fair Value Of Financial Instruments (Narrative) (Details)	9 Months Ended
	Sep. 30, 2011
Senior Notes [Member] | 5.50% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, interest rate	5.50%
Debt instrument interest rate traded percentage	98.20%
Debt instrument interest rate effective yield percentage	5.80%
Senior Notes [Member] | 7.50% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, interest rate	7.50%
Debt instrument interest rate traded percentage	114.30%
Debt instrument interest rate effective yield percentage	4.20%
5.50% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, interest rate	5.50%
7.50% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes, interest rate	7.50%