Employee Benefits - Schedule of Significant Unobservable Inputs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plan Asset
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets beginning balance	$ 1,499	$ 1,649
Actual return on assets	319	(97)
Fair value of plan assets ending balance	1,747	1,499
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets beginning balance	17
Fair value of plan assets ending balance		17
Level 3 | Pension Plan Asset
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets beginning balance	230
Purchases, issuances and settlements, net	94	(25)
Fair value of plan assets ending balance	349	230
Level 3 | Pension Plan Asset | Guaranteed Annuity Contracts And Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plan assets beginning balance	230	278
Actual return on assets	25	(23)
Fair value of plan assets ending balance	$ 349	$ 230