Benefit Obligations (Plan Assets Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		7.80%	8.20%	8.00%
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year		$ 23
United States Pension Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets		(2.50%)
Expected return on plan assets		8.00%	8.50%	8.50%
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year		$ 5
Nonqualified Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year		$ 22
Scenario, Forecast [Member] | United States Pension Plan of US Entity [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets	7.50%