Pension and Other Postretirement Employee Benefit Plans - Twenty-Five Basis Point Decrease Effects (Details) - Defined benefit pension plans - U.S. $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expected long-term rate of return on plan assets, next fiscal year	3.00%
Discount rate, next fiscal year	2.50%
Pension expense
Expected long-term rate of return	$ 43
Discount rate	(20)
Benefit obligation
Discount rate	$ 404