Environmental (Details) $ in Millions	3 Months Ended			12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($) sites	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Environmental Issue [Member]
Loss Contingencies [Line Items]
Increase in environmental expense	$ 8	$ 7	$ 5
Environmental Issue [Member]
Loss Contingencies [Line Items]
Number of alleged environmental contamination sites (in sites) | sites				220
Number of environmental superfund sites (in sites) | sites				18
Liability for third-party tort claims				$ 12	$ 12
Estimated time frame for accrued cost distributions				10 years
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance				$ 369	404	$ 435
Accruals				5	4	13
Payments				(32)	(39)	(44)
Ending balance				342	369	$ 404
Environmental Issue [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Future costs to settle claims and associated liability				275
Environmental Issue [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Future costs to settle claims and associated liability				480
Environmental Issue [Member] | Current Liabilities [Member]
Loss Contingencies [Line Items]
Accrued obligations for environmental matters, current liabilities				$ 40	$ 50