Schedule of Significant Unobservable Inputs (Details) - Pension Plan Asset - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	$ 1,376	$ 1,428
Actual return on assets	99	(21)
Fair value of plan assets ending balance	1,443	1,376
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	136
Purchases, issuances and settlements, net	(4)	(3)
Fair value of plan assets ending balance	140	136
Level 3 | Guaranteed Annuity Contracts And Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets beginning balance	136	127
Actual return on assets	8	12
Fair value of plan assets ending balance	$ 140	$ 136