Employee Benefit Plans - Schedule of Reconciliation to Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	$ 177	$ 117
Net prior service cost (credit)	20	0
Total	197	117
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial loss (gain)	(29)	(16)
Net prior service cost (credit)	(18)	(25)
Total	$ (47)	$ (41)