Collateral Financing Arrangements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2007
Parent Company
Collateral Financing Arrangements (Textuals) [Abstract]
Interest expense	$ 920	$ 907	$ 829
MRC [Member] | Secured Debt [Member]
Collateral Financing Arrangements (Textuals) [Abstract]
Interest expense	38	44	22
Debt Instrument, Face Amount				$ 2,500
Debt Instrument, Term in Years				35 years
Partial repurchase	161	79	50
Increase (Decrease) in Other Receivables	23	8	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	$ 23	$ 8	$ 7
MRC [Member] | Parent Company | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	compounded SOFR calculated in arrears plus a spread adjustment of 0.26161%			three-month LIBOR plus 1.12%
MRC [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	three-month tenor plus a spread adjustment of 0.26161%			three-month London Interbank Offered Rate (“LIBOR”) plus 0.55%