Employee Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost	$ 1	$ 1	$ 2	$ 2
Interest cost	5	11	18	30
Expected return on plan assets	(6)	(12)	(17)	(34)
Amortization of net loss	7	4	18	14
Net periodic pension cost	7	4	21	12
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost	0	0	0	0
Interest cost	2	2	4	5
Expected return on plan assets	0	0	0	0
Amortization of net loss	0	1	2	2
Net periodic pension cost	$ 2	$ 3	$ 6	$ 7