Asset Retirement Obligations and Accrued Environmental Costs - Textuals (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Environmental Liabilities [Line Items]
Accrued environmental costs	$ 247	$ 258
Additional Asset Retirement Obligations and Accrued Environmental Costs (Textual) [Abstract]
Maximum number of years accrued environmental liabilities will be paid over	30 years
Expected expenditures for acquired environmental obligations, weighted-average discount factor rate	5.00%
Accrued environmental costs, undiscounted due within one year	$ 9
Accrued environmental costs, undiscounted due within second year	12
Accrued environmental costs, undiscounted due within three year	8
Accrued environmental costs, undiscounted due within fourth year	5
Accrued environmental costs, undiscounted due within fifth year	4
Accrued environmental costs, undiscounted due after fifth year	110
Cleanup Remediation Activities [Member]
Environmental Liabilities [Line Items]
Accrued environmental costs	183	184
Corporate and Other Environmental Liabilities [Member]
Environmental Liabilities [Line Items]
Accrued environmental costs	51	57
Federal Comprehensive Environmental Response Compensation and Liability Act or Similar State Laws [Member]
Environmental Liabilities [Line Items]
Accrued environmental costs	13	$ 17
Acquired Environmental Obligations [Member]
Environmental Liabilities [Line Items]
Discounted accrued environmental costs	$ 92