Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Oct. 21, 2002
Fair Value of Financial Instruments
Carrying Value	$ 4,693,004	$ 4,512,332
Fair Value	5,187,676	4,879,402	200,000
5.375% Senior Notes Due August 2012 [Member]
Fair Value of Financial Instruments
Carrying Value	274,604	273,977
Fair Value	281,188	291,500
6.15% Senior Notes Due February 2018 [Member]
Fair Value of Financial Instruments
Carrying Value	967,490	966,276
Fair Value	1,113,986	1,041,008
9.25% Senior Notes Due January 2019 [Member]
Fair Value of Financial Instruments
Carrying Value	1,125,000	1,125,000
Fair Value	1,419,514	1,393,943
5.00% senior notes due September 2020 [Member]
Fair Value of Financial Instruments
Carrying Value	697,343	697,037
Fair Value	734,475	678,335
4.625% senior notes due September 2021 [Member]
Fair Value of Financial Instruments
Carrying Value	697,667	0
Fair Value	708,176	0
0.94% Senior Exchangeable Notes Due May 2011 [Member]
Fair Value of Financial Instruments
Carrying Value	0	1,378,178
Fair Value	0	1,403,315
Subsidiary preferred stock [Member]
Fair Value of Financial Instruments
Carrying Value	69,188	69,188
Fair Value	68,625	68,625
Revolving Credit Facilities [Member]
Fair Value of Financial Instruments
Carrying Value	860,000	0
Fair Value	860,000	0
Other [Member]
Fair Value of Financial Instruments
Carrying Value	1,712	2,676
Fair Value	$ 1,712	$ 2,676