Pension Benefits Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Pension Plan, Postemployment Benefit Period	5 years
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 76
Defined Contribution Plan, Cost Recognized	$ 45	$ 51	$ 55