Employee Benefits - Overview of the accumulated benefit obligation, fair value of plan assets, funded status and net amount recognized for U.S. and Canadian Other Post-Retirement Benefits (Details) - Other Post-Retirement Benefits - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated projected benefit obligation	$ 117	$ 103
Fair value of plan assets	17	16
Funded status	(100)	(87)
Unrecognized prior-service credit	(1)	(1)
Unrecognized loss	13	3
Net amount recognized	$ (88)	$ (85)