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Debt (Long-Term Debt) (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 2,229 | $ 2,228
Debt issuance costs |  | 10 | 12
6.400% Senior Notes Due 2022 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 0 | 115
Long-term debt, interest rate |  | 6.40% |
Long-term debt, maturity year |  | 2022 |
7.000% Debentures Due 2025 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 46 | 46
Long-term debt, interest rate |  | 7.00% |
Long-term debt, maturity year |  | 2025 |
7.150% Debentures Due 2027 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 100 | 100
Long-term debt, interest rate |  | 7.15% |
Long-term debt, maturity year |  | 2027 |
6.625% Debentures Due 2028 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 141 | 141
Long-term debt, interest rate |  | 6.625% |
Long-term debt, maturity year |  | 2028 |
5.700% Senior Notes Due 2034 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross | [1] | $ 21 | 21
Long-term debt, interest rate |  | 5.70% |
Long-term debt, maturity year |  | 2034 |
Surplus Notes due 2033 [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Surplus notes outstanding | [2] | $ 940 | 940
Long-term debt, maturity year |  | 2033 |
Accrued Interest [Member] |  |  |
Debt Instrument [Line Items] |  |  |
Long-term debt, gross |  | $ 991 | $ 877
[1] | Callable anytime at the greater of par or the present value of the remaining scheduled payments of principal and interest.
[2] | Contractual interest rate is based on three month LIBOR plus 11.26%.

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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details
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