Employee Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost			$ 1	$ 1
Interest cost	$ 9	$ 10	19	20
Expected return on plan assets	(11)	(12)	(22)	(24)
Amortization of net loss	6	5	10	9
Net periodic pension cost	4	3	8	6
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost			0	0
Interest cost	2	2	3	3
Expected return on plan assets	0	0	0	0
Amortization of net loss	0	0	1	1
Net periodic pension cost	$ 2	$ 2	$ 4	$ 4