Comprehensive Income (Loss) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Discount rate - used at year end to value obligation	3.80%	3.80%	4.10%
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement	$ (28)	$ 20
Other comprehensive income, Recognition of net actuarial loss for pension settlement costs, before tax		62
Pension Costs [Member] | Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, Recognition of net actuarial loss for pension settlement costs, before tax		62
Pension Costs [Member] | Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, Recognition of net actuarial loss for pension settlement costs, before tax		62
Other Comprehensive Income, Recognition Of Net Actuarial Loss For Pension Settlement Costs, Net of Tax		$ 36