Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for doubtful accounts receivable
Reserves and allowances deducted from asset accounts
Balance at the beginning of the period	$ 38	$ 65	$ 114
Charge to cost and expenses		5	27
Deductions	10	32	76
Balance at the end of the period	28	38	65
Allowance for obsolete materials and supplies
Reserves and allowances deducted from asset accounts
Balance at the beginning of the period	70	66	49
Charge to cost and expenses	5	6	17
Deductions	2	2
Balance at the end of the period	73	70	66
Deductions resulting from sale of rigs and inventory		1
Deductions resulting from loss of Deepwater Horizon		1
Valuation allowance on deferred tax assets
Reserves and allowances deducted from asset accounts
Balance at the beginning of the period	164	160	111
Charge to cost and expenses	19	8	49
Deductions		4
Balance at the end of the period	$ 183	$ 164	$ 160