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Employee Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2008
Defined Benefit Plans and Other Postretirement Benefit Plans
Minimum participant age to elect				40 years
Employer discretionary contribution amount	$ 22	$ 19	$ 18
Requisite service period	3 years
Actual return on plan assets	11.40%	24.50%
Pension plan assets at fair value	$ 357	$ 354	318
Employee Stock
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension plan assets, shares	29,776
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans
Matching contribution to defined contribution plan	6.00%
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Percentage of increase decrease in benefit obligations discount rate	0.72%
Change In Net Benefit Cost Discount Rate Assumption	0.94%
Pension Plan \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans
Cash dividends paid (less than $1 million)	$ 1	1
Supplemental Employee Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Accrued employee benefit	$ 10	11
Percentage of increase decrease in benefit obligations discount rate	0.81%
Change In Net Benefit Cost Discount Rate Assumption	0.92%
Expected contribution by employer during 2021	$ 8
Top Hat Savings Plan - Mutual Funds and Common Equities
Defined Benefit Plans and Other Postretirement Benefit Plans
CFC Top Hat Savings Plan	51	45
Top Hat \| Top Hat Savings Plan - Mutual Funds and Common Equities
Defined Benefit Plans and Other Postretirement Benefit Plans
CFC Top Hat Savings Plan	51	45
Top Hat \| Top Hat Savings Plan - Mutual Funds and Common Equities \| Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans
Employer discretionary contribution amount	$ 1	$ 1	$ 1
Domestic Corporate Debt Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension plan assets, shares	202,337	232,113
Pension plan assets, fair value	$ 18	$ 24
Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	82.00%
Pension plan assets at fair value	$ 266	260
Equity Securities \| Information Technology Sector
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	26.00%
Equity Securities \| Financial Services Sector
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	20.00%
Equity Securities \| Industrial Sector
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	13.00%
Equity Securities \| Healthcare Sector
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	12.00%
Equity Securities \| All Remaining Sectors
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	10.00%
Fixed Maturities
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension plan assets at fair value	$ 60	77
Fixed Maturities \| United States Government
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	9.00%
Pension plan assets at fair value	$ 31	25
Fixed Maturities \| Domestic Corporate Debt Securities
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	6.00%
Pension plan assets at fair value	$ 20	27
Fixed Maturities \| States, Municipalities and Political Subdivisions
Defined Benefit Plans and Other Postretirement Benefit Plans
Allocation percentage of investments	3.00%
Pension plan assets at fair value	$ 9	25
Cash and Cash Equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans
Pension plan assets at fair value	$ 31	$ 17