Pension Plans - Defined benefit plan (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Change in benefit obligation:
Interest cost	$ 108,000,000	$ 129,000,000
Components of net periodic pension benefit
Interest cost	108,000,000	129,000,000
Expected return on plan assets	(185,000,000)	(181,000,000)
Recognized net actuarial loss	41,000,000	35,000,000
Total net periodic pension benefit	(36,000,000)	$ (17,000,000)
Minimum required pension contributions for 2020	$ 0