Fair Value Measurements (Details 1) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair Value of Financial Instruments
Carrying Value	$ 4,334,655	$ 4,512,332
Fair Value	4,778,700	4,879,402
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
6.15% Senior Notes Due February 2018 [Member]
Fair Value of Financial Instruments
Carrying Value	966,883	966,276
Fair Value	1,083,050	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	1,436,738	1,393,943
5.00% senior notes due September 2020 [Member]
Fair Value of Financial Instruments
Carrying Value	697,190	697,037
Fair Value	700,308	678,335
5.375% Senior Notes Due August 2012 [Member]
Fair Value of Financial Instruments
Carrying Value	274,291	273,977
Fair Value	287,876	291,500
Subsidiary preferred stock [Member]
Fair Value of Financial Instruments
Carrying Value	69,188	69,188
Fair Value	68,625	68,625
Revolving Credit Facility [Member]
Fair Value of Financial Instruments
Carrying Value	1,200,000	0
Fair Value	1,200,000	0
Other [Member]
Fair Value of Financial Instruments
Carrying Value	2,103	2,676
Fair Value	$ 2,103	$ 2,676