Insurance Premiums (Unearned Premium Revenue Balance And Future Expected Earnings) (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Insurance Premiums [Line Items]
Total Expected Future Premium Earnings	$ 271
Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Unearned Premiums	232
Upfront [Member]
Insurance Premiums [Line Items]
Total Expected Future Premium Earnings	99
Installments [Member]
Insurance Premiums [Line Items]
Total Expected Future Premium Earnings	133
Accretion [Member]
Insurance Premiums [Line Items]
Total Expected Future Premium Earnings	39
March Thirty One Two Thousand Twenty Four [Member]
Insurance Premiums [Line Items]
Three months ending, March 31, 2024, Total Expected Future Premium Earnings	9
March Thirty One Two Thousand Twenty Four [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Three months ending, March 31, 2024, Total Expected Future Premium Earnings	224
March Thirty One Two Thousand Twenty Four [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Three months ending, March 31, 2024, Total Expected Future Premium Earnings	4
March Thirty One Two Thousand Twenty Four [Member] | Installments [Member]
Insurance Premiums [Line Items]
Three months ending, March 31, 2024, Total Expected Future Premium Earnings	4
March Thirty One Two Thousand Twenty Four [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Three months ending, March 31, 2024, Total Expected Future Premium Earnings	1
June Thirty Two Thousand Twenty Four [Member]
Insurance Premiums [Line Items]
Three months ending, June 30, 2024, Total Expected Future Premium Earnings	8
June Thirty Two Thousand Twenty Four [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Three months ending, June 30, 2024, Total Expected Future Premium Earnings	217
June Thirty Two Thousand Twenty Four [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Three months ending, June 30, 2024, Total Expected Future Premium Earnings	3
June Thirty Two Thousand Twenty Four [Member] | Installments [Member]
Insurance Premiums [Line Items]
Three months ending, June 30, 2024, Total Expected Future Premium Earnings	4
June Thirty Two Thousand Twenty Four [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Three months ending, June 30, 2024, Total Expected Future Premium Earnings	1
September Thirty Two Thousand Twenty Four [Member]
Insurance Premiums [Line Items]
Three months ending, September 30, 2024, Total Expected Future Premium Earnings	8
September Thirty Two Thousand Twenty Four [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Three months ending, September 30, 2024, Total Expected Future Premium Earnings	210
September Thirty Two Thousand Twenty Four [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Three months ending, September 30, 2024, Total Expected Future Premium Earnings	3
September Thirty Two Thousand Twenty Four [Member] | Installments [Member]
Insurance Premiums [Line Items]
Three months ending, September 30, 2024, Total Expected Future Premium Earnings	4
September Thirty Two Thousand Twenty Four [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Three months ending, September 30, 2024, Total Expected Future Premium Earnings	1
December Thirty One Two Thousand Twenty Four [Member]
Insurance Premiums [Line Items]
Three months ending, December 31, 2024, Total Expected Future Premium Earnings	8
December Thirty One Two Thousand Twenty Four [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Three months ending, December 31, 2024, Total Expected Future Premium Earnings	203
December Thirty One Two Thousand Twenty Four [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Three months ending, December 31, 2024, Total Expected Future Premium Earnings	3
December Thirty One Two Thousand Twenty Four [Member] | Installments [Member]
Insurance Premiums [Line Items]
Three months ending, December 31, 2024, Total Expected Future Premium Earnings	4
December Thirty One Two Thousand Twenty Four [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Three months ending, December 31, 2024, Total Expected Future Premium Earnings	1
December Thirty One Two Thousand Twenty Five [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2025, Total Expected Future Premium Earnings	29
December Thirty One Two Thousand Twenty Five [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2025, Total Expected Future Premium Earnings	178
December Thirty One Two Thousand Twenty Five [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2025, Total Expected Future Premium Earnings	12
December Thirty One Two Thousand Twenty Five [Member] | Installments [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2025, Total Expected Future Premium Earnings	13
December Thirty One Two Thousand Twenty Five [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2025, Total Expected Future Premium Earnings	4
December Thirty One Two Thousand Twenty Six [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2026, Total Expected Future Premium Earnings	25
December Thirty One Two Thousand Twenty Six [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2026, Total Expected Future Premium Earnings	156
December Thirty One Two Thousand Twenty Six [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2026, Total Expected Future Premium Earnings	11
December Thirty One Two Thousand Twenty Six [Member] | Installments [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2026, Total Expected Future Premium Earnings	11
December Thirty One Two Thousand Twenty Six [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2026, Total Expected Future Premium Earnings	3
December Thirty One Two Thousand Twenty Seven [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2027, Total Expected Future Premium Earnings	21
December Thirty One Two Thousand Twenty Seven [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2027, Total Expected Future Premium Earnings	138
December Thirty One Two Thousand Twenty Seven [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2027, Total Expected Future Premium Earnings	9
December Thirty One Two Thousand Twenty Seven [Member] | Installments [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2027, Total Expected Future Premium Earnings	9
December Thirty One Two Thousand Twenty Seven [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2027, Total Expected Future Premium Earnings	3
December Thirty One Two Thousand Twenty Eight [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2028, Total Expected Future Premium Earnings	19
December Thirty One Two Thousand Twenty Eight [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2028, Total Expected Future Premium Earnings	122
December Thirty One Two Thousand Twenty Eight [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2028, Total Expected Future Premium Earnings	8
December Thirty One Two Thousand Twenty Eight [Member] | Installments [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2028, Total Expected Future Premium Earnings	8
December Thirty One Two Thousand Twenty Eight [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Twelve months ending, December 31, 2028, Total Expected Future Premium Earnings	3
December Thirty One Two Thousand Twenty Thirty Three [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2033, Total Expected Future Premium Earnings	70
December Thirty One Two Thousand Twenty Thirty Three [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2033, Total Expected Future Premium Earnings	63
December Thirty One Two Thousand Twenty Thirty Three [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2033, Total Expected Future Premium Earnings	27
December Thirty One Two Thousand Twenty Thirty Three [Member] | Installments [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2033, Total Expected Future Premium Earnings	32
December Thirty One Two Thousand Twenty Thirty Three [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2033, Total Expected Future Premium Earnings	11
December Thirty One Two Thousand Twenty Thirty Eight [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2038, Total Expected Future Premium Earnings	40
December Thirty One Two Thousand Twenty Thirty Eight [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2038, Total Expected Future Premium Earnings	30
December Thirty One Two Thousand Twenty Thirty Eight [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2038, Total Expected Future Premium Earnings	11
December Thirty One Two Thousand Twenty Thirty Eight [Member] | Installments [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2038, Total Expected Future Premium Earnings	22
December Thirty One Two Thousand Twenty Thirty Eight [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2038, Total Expected Future Premium Earnings	7
December Thirty One Two Thousand Fourty Three And Thereafter [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2043 and thereafter, Total Expected Future Premium Earnings	34
December Thirty One Two Thousand Fourty Three And Thereafter [Member] | Unearned Premium Revenue [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2043 and thereafter, Total Expected Future Premium Earnings	0
December Thirty One Two Thousand Fourty Three And Thereafter [Member] | Upfront [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2043 and thereafter, Total Expected Future Premium Earnings	8
December Thirty One Two Thousand Fourty Three And Thereafter [Member] | Installments [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2043 and thereafter, Total Expected Future Premium Earnings	22
December Thirty One Two Thousand Fourty Three And Thereafter [Member] | Accretion [Member]
Insurance Premiums [Line Items]
Five years ending, December 31, 2043 and thereafter, Total Expected Future Premium Earnings	$ 4