Senior Notes And Other Debt (Schedule of Debt) (Details) (USD $)	Dec. 31, 2011		Dec. 31, 2010
Debt Instrument [Line Items]
Face Value	$ 1,510,829,000
Total debt, carrying value	1,500,503,000		1,500,419,000
Senior Notes due February 15, 2013 [Member]
Debt Instrument [Line Items]
Face Value	200,000,000
Carrying Value	199,627,000		199,295,000
Rate	5.875%
Senior Notes due May 15, 2015 [Member]
Debt Instrument [Line Items]
Face Value	200,000,000
Carrying Value	199,373,000		199,187,000
Rate	5.60%
Senior Notes due August 15, 2019 [Member]
Debt Instrument [Line Items]
Face Value	150,000,000
Carrying Value	148,914,000		148,772,000
Rate	6.15%
Senior Notes due September 15, 2019 [Member]
Debt Instrument [Line Items]
Face Value	300,000,000
Carrying Value	298,038,000		297,784,000
Rate	7.375%
Senior Notes due September 15, 2020 [Member]
Debt Instrument [Line Items]
Face Value	300,000,000
Carrying Value	297,065,000		296,729,000
Rate	5.375%
Senior Notes due January 1, 2022 [Member]
Debt Instrument [Line Items]
Face Value	76,503,000
Carrying Value	75,924,000		75,890,000
Rate	8.70%
Senior Notes due February 15, 2037 [Member]
Debt Instrument [Line Items]
Face Value	250,000,000
Carrying Value	247,236,000		247,126,000
Rate	6.25%
Subsidiary Debt, Various due dates, 2012 [Member]
Debt Instrument [Line Items]
Carrying Value	4,000,000	[1]
Subsidiary Debt, Various due dates, 2013 [Member]
Debt Instrument [Line Items]
Carrying Value	1,000,000	[1]
Subsidiary Debt, Various due dates, 2014 [Member]
Debt Instrument [Line Items]
Carrying Value	26,000,000	[1]
Subsidiary Debt, Various due dates, Thereafter [Member]
Debt Instrument [Line Items]
Carrying Value	3,000,000	[1]
Subsidiary Debt [Member]
Debt Instrument [Line Items]
Face Value	34,326,000	[1]
Carrying Value	$ 34,326,000	[1]	$ 35,636,000	[1]

[1] Subsidiary debt is due as follows: $4 million in 2012, $1 million in 2013, $26 million in 2014 and $3 million thereafter.