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Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Segment Reporting Information [Line Items] |  |  |  |  |  |
Revenues | [1] | $ 77 |  | $ 103 |  |
Net change in fair value of insured derivatives |  | (5) |  | (53) |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (9) |  | 17 |  |
Net investment losses related to other-than-temporary impairments |  | (1) |  | (2) |  |
Net gains (losses) on extinguishment of debt |  | 0 |  | 8 |  |
Other net realized gains (losses) |  | (1) |  | 3 |  |
Revenues of consolidated VIEs |  | 12 |  | 1 |  |
Inter-segment revenues | [2] | 0 |  | 0 |  |
Total revenues |  | 73 |  | 77 |  |
Losses and loss adjustment |  | 72 |  | 94 |  |
Operating |  | 24 |  | 36 |  |
Interest |  | 51 |  | 48 |  |
Expenses of consolidated VIEs |  | 22 |  | 19 |  |
Inter-segment expenses | [2] | 0 |  | 0 |  |
Total expenses |  | 169 |  | 197 |  |
Income (loss) before income taxes |  | (96) |  | (120) |  |
Provision (benefit) for income taxes |  | 2 |  | (48) |  |
Net income (loss) |  | (98) |  | (72) |  |
Identifiable assets |  | 8,893 |  | 11,017 |  | $ 9,095
U S Public Finance Insurance [Member] |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Losses and loss adjustment |  | 77 |  | 11 |  |
Operating Segments [Member] | U S Public Finance Insurance [Member] |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Revenues | [1] | 53 |  | 68 |  |
Net change in fair value of insured derivatives |  | 0 |  | 0 |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (6) |  | 4 |  |
Net investment losses related to other-than-temporary impairments |  | (1) |  | (2) |  |
Net gains (losses) on extinguishment of debt |  | 0 |  | 0 |  |
Other net realized gains (losses) |  | 0 |  | 0 |  |
Revenues of consolidated VIEs |  | 0 |  | 0 |  |
Inter-segment revenues | [2] | 7 |  | 5 |  |
Total revenues |  | 53 |  | 75 |  |
Losses and loss adjustment |  | 77 |  | 11 |  |
Operating |  | 3 |  | 10 |  |
Interest |  | 0 |  | 0 |  |
Expenses of consolidated VIEs |  | 0 |  | 0 |  |
Inter-segment expenses | [2] | 15 |  | 15 |  |
Total expenses |  | 95 |  | 36 |  |
Income (loss) before income taxes |  | (42) |  | 39 |  |
Provision (benefit) for income taxes |  | (9) |  | 12 |  |
Net income (loss) |  | (33) |  | 27 |  |
Identifiable assets |  | 4,508 |  | 5,128 |  |
Operating Segments [Member] | Corporate Operations [Member] |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Revenues | [1] | 7 |  | 8 |  |
Net change in fair value of insured derivatives |  | 0 |  | 0 |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | 3 |  | 16 |  |
Net investment losses related to other-than-temporary impairments |  | 0 |  | 0 |  |
Net gains (losses) on extinguishment of debt |  | 0 |  | 8 |  |
Other net realized gains (losses) |  | (2) |  | (1) |  |
Revenues of consolidated VIEs |  | 0 |  | 0 |  |
Inter-segment revenues | [2] | 13 |  | 16 |  |
Total revenues |  | 21 |  | 47 |  |
Losses and loss adjustment |  | 0 |  | 0 |  |
Operating |  | 13 |  | 18 |  |
Interest |  | 20 |  | 22 |  |
Expenses of consolidated VIEs |  | 0 |  | 0 |  |
Inter-segment expenses | [2] | 6 |  | 1 |  |
Total expenses |  | 39 |  | 41 |  |
Income (loss) before income taxes |  | (18) |  | 6 |  |
Provision (benefit) for income taxes |  | (33) |  | (4) |  |
Net income (loss) |  | 15 |  | 10 |  |
Identifiable assets |  | 1,159 |  | 2,335 |  |
Operating Segments [Member] | International And Structured Finance Insurance [Member] |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Revenues | [1] | 17 |  | 27 |  |
Net change in fair value of insured derivatives |  | (5) |  | (53) |  |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (6) |  | (3) |  |
Net investment losses related to other-than-temporary impairments |  | 0 |  | 0 |  |
Net gains (losses) on extinguishment of debt |  | 0 |  | 0 |  |
Other net realized gains (losses) |  | 1 |  | 4 |  |
Revenues of consolidated VIEs |  | 12 |  | 1 |  |
Inter-segment revenues | [2] | 7 |  | 9 |  |
Total revenues |  | 26 |  | (15) |  |
Losses and loss adjustment |  | (5) |  | 83 |  |
Operating |  | 8 |  | 8 |  |
Interest |  | 31 |  | 26 |  |
Expenses of consolidated VIEs |  | 22 |  | 19 |  |
Inter-segment expenses | [2] | 6 |  | 14 |  |
Total expenses |  | 62 |  | 150 |  |
Income (loss) before income taxes |  | (36) |  | (165) |  |
Provision (benefit) for income taxes |  | (5) |  | (57) |  |
Net income (loss) |  | (31) |  | (108) |  |
Identifiable assets |  | 5,359 |  | 6,502 |  |
Intersegment Elimination [Member] |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Inter-segment revenues | [2] | (27) |  | (30) |  |
Total revenues |  | (27) |  | (30) |  |
Inter-segment expenses | [2] | (27) |  | (30) |  |
Total expenses |  | (27) |  | (30) |  |
Income (loss) before income taxes |  | 0 |  | 0 |  |
Provision (benefit) for income taxes |  | 49 |  | 1 |  |
Net income (loss) |  | (49) |  | (1) |  |
Identifiable assets |  | $ (2,133) | [3] | $ (2,948) | [4] |
[1] | Represents the sum of third-party financial guarantee net premiums earned, net investment income, insurance-related fees and reimbursements and other fees.
[2] | Represents intercompany premium income and expense and intercompany interest income and expense pertaining to intercompany receivables and payables.
[3] | Consists of intercompany reinsurance balances and repurchase agreements.
[4] | Consists of intercompany deferred income taxes, reinsurance balances and repurchase agreements.

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