Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Income Taxes Paid Net, Discontinued Operations			$ 1,312
Operating activities:
Interest paid (net of amounts capitalized)	$ (375)	$ (325)	(279)
Income taxes paid to taxing authorities	(84)	(171)	(1,679)
Commercial paper:
Issuances	0	0	2,345
Repayments	0	0	(2,480)
Net commercial paper	0	0	(135)
Noncash investing and financing activities:
Asset retirement costs capitalized, excluding acquisitions	111	(85)	151
Increase in capital expenditure accrual		0	335
Asset Retirement Obligation, Liabilities Transferred	$ 40	$ 251	$ 359