Debt (Summary Of Company's Senior Notes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument
Senior note carrying value	$ 2,058,168	$ 2,509,613
Estimated fair value	2,070,744	2,663,451
Unsecured Senior Notes 5.25% Due January 2014 [Member]
Debt Instrument
Senior note carrying value	0	187,970
Debt instrument, interest rate, stated percentage	5.25%	5.25%
Debt instrument, maturity date, description	January 2014	January 2014
Unsecured Senior Notes 5.70% Due May 2014 [Member]
Debt Instrument
Senior note carrying value	0	208,274
Debt instrument, interest rate, stated percentage	5.70%	5.70%
Debt instrument, maturity date, description	May 2014	May 2014
Unsecured Senior Notes 5.20% Due February 2015 [Member]
Debt Instrument
Senior note carrying value	95,633	95,615
Debt instrument, interest rate, stated percentage	5.20%	5.20%
Debt instrument, maturity date, description	February 2015	February 2015
Unsecured Senior Notes 5.25% Due June 2015 [Member]
Debt Instrument
Senior note carrying value	233,085	264,058
Debt instrument, interest rate, stated percentage	5.25%	5.25%
Debt instrument, maturity date, description	June 2015	June 2015
Unsecured Senior Notes 6.50% Due May 2016 [Member]
Debt Instrument
Senior note carrying value	459,581	457,154
Debt instrument, interest rate, stated percentage	6.50%	6.50%
Debt instrument, maturity date, description	May 2016	May 2016
Unsecured Senior Notes 7.625% Due October 2017 [Member]
Debt Instrument
Senior note carrying value	122,663	149,481
Debt instrument, interest rate, stated percentage	7.625%	7.625%
Debt instrument, maturity date, description	October 2017	October 2017
Unsecured Senior Notes 7.875% Due June 2032 [Member]
Debt Instrument
Senior note carrying value	299,196	299,152
Debt instrument, interest rate, stated percentage	7.875%	7.875%
Debt instrument, maturity date, description	June 2032	June 2032
Unsecured Senior Notes 6.375% Due May 2033 [Member]
Debt Instrument
Senior note carrying value	398,567	398,492
Debt instrument, interest rate, stated percentage	6.375%	6.375%
Debt instrument, maturity date, description	May 2033	May 2033
Unsecured Senior Notes 6.00% Due February 2035 [Member]
Debt Instrument
Senior note carrying value	299,443	299,417
Debt instrument, interest rate, stated percentage	6.00%	6.00%
Debt instrument, maturity date, description	February 2035	February 2035
Unsecured Senior Notes 7.375% Due June 2046 [Member]
Debt Instrument
Senior note carrying value	$ 150,000	$ 150,000
Debt instrument, interest rate, stated percentage	7.375%	7.375%
Debt instrument, maturity date, description	June 2046	June 2046