Retirement Plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net Periodic Pension And OPEB Cost [Abstract]
Changes in fair value			5 years
Other comprehensive income defined benefit plans	$ (24,000,000)	$ (18,000,000)	$ (49,000,000)	$ (40,000,000)
Defined Benefit Plans [Member]
Net Periodic Pension And OPEB Cost [Abstract]
Service cost	30,000,000	26,000,000	60,000,000	53,000,000
Interest cost	27,000,000	35,000,000	53,000,000	69,000,000
Expected return on plan assets	(68,000,000)	(70,000,000)	(135,000,000)	(140,000,000)
Amortization of actuarial loss	35,000,000	24,000,000	71,000,000	52,000,000
Net periodic cost	24,000,000	15,000,000	49,000,000	34,000,000
Voluntary cash contributions to qualified pension plan			0
OPEB [Member]
Net Periodic Pension And OPEB Cost [Abstract]
Service cost	1,000,000	1,000,000	1,000,000	1,000,000
Interest cost	1,000,000	2,000,000	2,000,000	3,000,000
Amortization of prior service cost	(3,000,000)	(4,000,000)	(7,000,000)	(7,000,000)
Amortization of actuarial loss	$ 1,000,000	2,000,000	3,000,000	4,000,000
Net periodic cost		$ 1,000,000	$ (1,000,000)	$ 1,000,000