Goodwill and Other Intangible Assets (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Change in gross carrying amounts of definite-lived intangible assets
Gross carrying amount at the beginning of the period	$ 339	$ 339
Gross carrying amount at the end of the period	339	339
Changes in accumulated amortization and impairment of finite-lived intangible liabilities
Accumulated amortization and impairment at the beginning of the period	(274)	(251)
Amortization	(11)	(23)
Accumulated amortization and impairment at the end of the period	(285)	(274)
Net carrying amount at the beginning of the period	65	88
Net carrying amount at the end of the period	54	65
Drilling contract intangible assets
Change in gross carrying amounts of definite-lived intangible assets
Gross carrying amount at the beginning of the period	191	191
Gross carrying amount at the end of the period	191	191
Changes in accumulated amortization and impairment of finite-lived intangible liabilities
Accumulated amortization and impairment at the beginning of the period	(185)	(167)
Amortization	(6)	(18)
Accumulated amortization and impairment at the end of the period	(191)	(185)
Net carrying amount at the beginning of the period	6	24
Net carrying amount at the end of the period		6
Customer relationships
Change in gross carrying amounts of definite-lived intangible assets
Gross carrying amount at the beginning of the period	148	148
Gross carrying amount at the end of the period	148	148
Changes in accumulated amortization and impairment of finite-lived intangible liabilities
Accumulated amortization and impairment at the beginning of the period	(89)	(84)
Amortization	(5)	(5)
Accumulated amortization and impairment at the end of the period	(94)	(89)
Net carrying amount at the beginning of the period	59	64
Net carrying amount at the end of the period	54	59
Drilling contract intangible liabilities
Changes in accumulated amortization and impairment of finite-lived intangible liabilities
Accumulated amortization and impairment at the beginning of the period	(1,342)	(1,226)
Amortization	(51)	(116)
Accumulated amortization and impairment at the end of the period	(1,393)	(1,342)
Gross carrying amount at the beginning of the period	1,494	1,494
Gross carrying amount at the end of the period	1,494	1,494
Net carrying amount at the beginning of the year	152	268
Amortization	(51)	(116)
Net carrying amount at the end of the year	$ 101	$ 152