Retirement Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Rate of employee contribution from earnings	80.00%
Matching contribution allocation rate first time	100.00%
Employee contribution rate for first time matching	3.00%
Matching contribution allocation rate second time	50.00%
Employees contribution rate for second time matching	3.00%
Employer contribution in common stock	$ 31	$ 33	$ 29
Minimum range of eligible compensation for noncontributory profit sharing feature	0.00%
Maximum range of eligible compensation for noncontributory profit sharing feature	3.50%
Accrued profit sharing expense	$ 7	16	17
Debt Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets		166
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	28	1	1
Plan assets	0	171	157
Supplemental Employee Retirement Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	0	0	0
Benefit liability	5	5
Plan assets	$ 0	$ 0	$ 0