Fair Value Measurements (Details 1) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Fair Value of Financial Instruments
Carrying Value	$ 4,432,548	$ 4,512,332
Fair Value	4,881,601	4,879,402
5.375% Senior Notes Due August 2012 [Member]
Fair Value of Financial Instruments
Carrying Value	274,448	273,977
Fair Value	284,952	291,500
6.15% Senior Notes Due February 2018 [Member]
Fair Value of Financial Instruments
Carrying Value	967,186	966,276
Fair Value	1,078,984	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	1,438,864	1,393,943
5.00% senior notes due September 2020 [Member]
Fair Value of Financial Instruments
Carrying Value	697,266	697,037
Fair Value	721,070	678,335
4.625% senior notes due September 2021 [Member]
Fair Value of Financial Instruments
Carrying Value	697,607	0
Fair Value	687,253	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	600,000	0
Fair Value	600,000	0
Other [Member]
Fair Value of Financial Instruments
Carrying Value	1,853	2,676
Fair Value	$ 1,853	$ 2,676