Retirement Plans (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 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)	$ (73,000,000)	$ (58,000,000)
Defined Benefit Plans [Member]
Net Periodic Pension And OPEB Cost [Abstract]
Service cost	25,000,000	19,000,000	85,000,000	72,000,000
Interest cost	25,000,000	33,000,000	78,000,000	102,000,000
Expected return on plan assets	(67,000,000)	(71,000,000)	(202,000,000)	(211,000,000)
Amortization of actuarial loss	35,000,000	27,000,000	106,000,000	79,000,000
Net periodic cost	18,000,000	8,000,000	67,000,000	42,000,000
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
Interest cost		1,000,000	2,000,000	4,000,000
Amortization of prior service cost	(3,000,000)	(3,000,000)	(10,000,000)	(10,000,000)
Amortization of actuarial loss	2,000,000	1,000,000	5,000,000	$ 5,000,000
Net periodic cost	$ (1,000,000)	$ (1,000,000)	$ (2,000,000)