Employee Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost	$ 1	$ 1
Interest cost	6	10
Expected return on plan assets	(6)	(11)
Amortization of net loss	6	4
Net periodic pension cost	7	4
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization of net loss	1	1
Net periodic pension cost	$ 2	$ 2