The amount transferred to(from) the trust from(to) the general account.

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Cash received (paid) in connection with the change in market value of collateral used to secure debt.

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Collateral Financing Arrangements.

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No definition available.

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Debt Instrument, Term in Years.

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No definition available.

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Face (par) amount of debt instrument at time of issuance.

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Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of increase (decrease) in receivables classified as other.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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Collateral Financing Arrangements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2007
Collateral Financing Arrangements (Textuals) [Abstract]
Debt Instrument, Face Amount		$ 3,200
AmountTransferredTo(From)TheTrust	$ (78)	2	$ 97
Parent Company
Collateral Financing Arrangements (Textuals) [Abstract]
Interest expense	833	850	1,009
MRC [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms				three-month LIBOR plus 0.55%
Collateral Financing Arrangements (Textuals) [Abstract]
Interest expense	20	38	37
Debt Instrument, Face Amount				$ 2,500
Debt Instrument, Term in Years				35 years
Partial repurchase	148	67	61
Increase (Decrease) in Other Receivables	20	9	7
MRC [Member] \| Cash Received (Paid) Collateral Financing Arrangements MRC [Member]
Collateral Financing Arrangements (Textuals) [Abstract]
Cash Received (Paid) In Connection With Collateral Financing Arrangements	20	$ 9	$ 7
MRC [Member] \| Parent Company \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms				three-month LIBOR plus 1.12%
Cumulative Repayment [Member] \| MRC [Member] \| Secured Debt [Member]
Collateral Financing Arrangements (Textuals) [Abstract]
Partial repurchase	$ 1,700