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Fair Value Of Financial Instruments (Fair Value Hierarchy Table Presents The Company's Assets And Liabilities At Fair Value Not Recorded On The Company's Consolidated Balance Sheet) (Detail) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Total liabilities |  | $ 1,459
Variable Interest Entity Primary Beneficiary [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Investments held-to-maturity, fair value | $ 925 | 916
Carrying Reported Amount Fair Value Disclosure [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Accrued investment income |  | 0
Payable for investments purchased |  | 0
Carrying Reported Amount Fair Value Disclosure [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Other investments | 1 | 2
Total assets | 891 | 892
Investment agreements | 311 | 337
Medium-term notes | 620 | 650
Long-term debt | 2,249 | 2,121
Total liabilities | 4,444 | 4,328
Gross | (43) | 1,220
Ceded | 35 | 39
Carrying Reported Amount Fair Value Disclosure [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Investments held-to-maturity, fair value | 890 | 890
Variable interest entity notes | 1,264 | 1,220
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Accrued investment income |  | 0
Payable for investments purchased |  | 0
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Other investments | 1 | 2
Total assets | 926 | 918
Investment agreements | 388 | 433
Medium-term notes | 422 | 406
Long-term debt | 1,101 | 1,002
Total liabilities | 3,214 | 3,109
Gross | 993 | 1,785
Ceded | 65 | 61
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Investments held-to-maturity, fair value | 925 | 916
Variable interest entity notes | 1,303 | 1,268
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 2 [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Accrued investment income |  | 0
Payable for investments purchased |  | 0
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Other investments | 1 | 2
Total assets | 1 | 2
Long-term debt | 1,101 | 1,002
Total liabilities | 1,479 | 1,354
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Variable interest entity notes | 378 | 352
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Total assets | 925 | 916
Investment agreements | 388 | 433
Medium-term notes | 422 | 406
Total liabilities | 1,735 | 1,755
Gross | 993 | 1,785
Ceded | 65 | 61
Fair Value [Member] | Value Disclosed At Fair Value Not Recorded At Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Fair Value Measurements Nonrecurring [Member] |  |
Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] |  |
Investments held-to-maturity, fair value | 925 | 916
Variable interest entity notes | $ 925 | $ 916

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- Definition Represents the Company's balance sheet carrying amount of the financial guarantee insurance contracts ceded to third party reinsurers. The balance sheet carrying amount comprises the prepaid reinsurance premiums and reinsurance recoverable on paid and unpaid losses + References No definition available. + Details
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- Definition Represents the Company's balance sheet carrying amount of the financial guarantee insurance contract obligations with third parties. The gross balance sheet carrying amount comprises the unearned premium revenue and the loss and loss adjustment expense reserves balances + References No definition available. + Details
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- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 + Details
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
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- Definition Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. + References Reference 1: 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(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: 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=6876686&loc=d3e534808-122878 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=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(13)) -URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996 + Details
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