Income Taxes (Exp) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Effective tax rate	(4.90%)	(12.80%)	(3.10%)
Components of provision (benefit) for income taxes
Current tax expense	$ (189)	$ 244	$ 5
Deferred tax expense (benefit)	248	(16)	89
Income tax expense	$ 59	228	94
Income tax expense reconciliation
Income tax expense (benefit) at Swiss federal statutory rate	7.83%
Income tax benefit at Swiss federal statutory rate	$ (94)	(139)	(235)
Earnings subject to rates different than the Swiss federal statutory rate	189	(86)	(30)
Changes in valuation allowance	37	67	162
Losses on impairment	35	114	241
Deemed profits taxes	22	8	16
Base erosion and anti-abuse tax	21	33
Withholding taxes	11	8	14
Currency revaluation of Norwegian assets	5	11	1
Effect of U.S. tax reform		104	66
Litigation matters, primarily related to the Macondo well incident			(70)
Benefit from foreign tax credits	(8)	(5)	(15)
Other, net	11	(4)
Income tax expense	59	228	94
Changes in unrecognized tax benefits, net	(268)	$ 117	$ (56)
U.S.
Income tax expense reconciliation
Other, net	$ 98