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Business Segments (Summary Of Company's Segment Results) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Revenues | [1] | $ 317 |  | $ 370 |  | $ 480 |
Net change in fair value of insured derivatives |  | (25) |  | (51) |  | (19) |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (17) |  | (24) |  | 84 |
Net investment losses related to other-than-temporary impairments |  | (5) |  | (106) |  | (5) |
Net gains (losses) on extinguishment of debt |  | 3 |  | 28 |  | 5 |
Other net realized gains (losses) |  | 0 |  | 31 |  | (282) |
Revenues of consolidated VIEs |  | (111) |  | 185 |  | 31 |
Inter-segment revenues | [2] | 0 |  | 0 |  | 0 |
Total revenues |  | 162 |  | 433 |  | 294 |
Losses and loss adjustment |  | 63 |  | 683 |  | 220 |
Operating |  | 91 |  | 129 |  | 177 |
Interest |  | 206 |  | 197 |  | 197 |
Expenses of consolidated VIEs |  | 98 |  | 85 |  | 39 |
Inter-segment expenses | [2] | 0 |  | 0 |  | 0 |
Total expenses |  | 458 |  | 1,094 |  | 633 |
Income (loss) before income taxes |  | (296) |  | (661) |  | (339) |
Identifiable assets |  | 8,076 |  | 9,095 |  | 11,137 |
U S Public Finance Insurance [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Losses and loss adjustment |  | 0 |  | 499 |  | 74 |
Operating Segments [Member] | U S Public Finance Insurance [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Revenues | [1] | 178 |  | 262 |  | 335 |
Net change in fair value of insured derivatives |  | 0 |  | 0 |  | 0 |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (20) |  | 25 |  | 72 |
Net investment losses related to other-than-temporary impairments |  | (5) |  | (106) |  | (4) |
Net gains (losses) on extinguishment of debt |  | 0 |  | 0 |  | 0 |
Other net realized gains (losses) |  | 0 |  | (4) |  | 2 |
Revenues of consolidated VIEs |  | 0 |  | 0 |  | 0 |
Inter-segment revenues | [2] | 29 |  | 23 |  | 22 |
Total revenues |  | 182 |  | 200 |  | 427 |
Losses and loss adjustment |  | 91 |  | 499 |  | 74 |
Operating |  | 18 |  | 36 |  | 40 |
Interest |  | 0 |  | 0 |  | 0 |
Expenses of consolidated VIEs |  | 0 |  | 0 |  | 0 |
Inter-segment expenses | [2] | 44 |  | 72 |  | 69 |
Total expenses |  | 153 |  | 607 |  | 183 |
Income (loss) before income taxes |  | 29 |  | (407) |  | 244 |
Identifiable assets |  | 4,203 |  | 4,582 |  | 5,077 |
Operating Segments [Member] | Corporate Operations [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Revenues | [1] | 31 |  | 30 |  | 24 |
Net change in fair value of insured derivatives |  | 0 |  | 0 |  | 0 |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | 22 |  | (32) |  | (14) |
Net investment losses related to other-than-temporary impairments |  | 0 |  | 0 |  | (1) |
Net gains (losses) on extinguishment of debt |  | 3 |  | 28 |  | 5 |
Other net realized gains (losses) |  | (2) |  | (4) |  | (5) |
Revenues of consolidated VIEs |  | 0 |  | 0 |  | 0 |
Inter-segment revenues | [2] | 45 |  | 60 |  | 58 |
Total revenues |  | 99 |  | 82 |  | 67 |
Losses and loss adjustment |  | 0 |  | 0 |  | 0 |
Operating |  | 47 |  | 59 |  | 80 |
Interest |  | 78 |  | 81 |  | 91 |
Expenses of consolidated VIEs |  | 0 |  | 0 |  | 0 |
Inter-segment expenses | [2] | 20 |  | 11 |  | 4 |
Total expenses |  | 145 |  | 151 |  | 175 |
Income (loss) before income taxes |  | (46) |  | (69) |  | (108) |
Identifiable assets |  | 1,192 |  | 1,312 |  | 2,479 |
Operating Segments [Member] | International And Structured Finance Insurance [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Revenues | [1] | 108 |  | 78 |  | 121 |
Net change in fair value of insured derivatives |  | (25) |  | (51) |  | (19) |
Net gains (losses) on financial instruments at fair value and foreign exchange |  | (19) |  | (17) |  | 26 |
Net investment losses related to other-than-temporary impairments |  | 0 |  | 0 |  | 0 |
Net gains (losses) on extinguishment of debt |  | 0 |  | 0 |  | 0 |
Other net realized gains (losses) |  | 2 |  | 39 |  | (279) |
Revenues of consolidated VIEs |  | (111) |  | 185 |  | 31 |
Inter-segment revenues | [2] | 24 |  | 44 |  | 51 |
Total revenues |  | (21) |  | 278 |  | (69) |
Losses and loss adjustment |  | (28) |  | 184 |  | 146 |
Operating |  | 26 |  | 34 |  | 57 |
Interest |  | 128 |  | 116 |  | 106 |
Expenses of consolidated VIEs |  | 98 |  | 85 |  | 39 |
Inter-segment expenses | [2] | 33 |  | 47 |  | 52 |
Total expenses |  | 257 |  | 466 |  | 400 |
Income (loss) before income taxes |  | (278) |  | (188) |  | (469) |
Identifiable assets |  | 4,742 |  | 5,404 |  | 6,486 |
Intersegment Elimination [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Inter-segment revenues | [2] | (98) |  | (127) |  | (131) |
Total revenues |  | (98) |  | (127) |  | (131) |
Inter-segment expenses | [2] | (97) |  | (130) |  | (125) |
Total expenses |  | (97) |  | (130) |  | (125) |
Income (loss) before income taxes |  | (1) |  | 3 |  | (6) |
Identifiable assets |  | $ (2,061) | [3] | $ (2,203) | [3] | $ (2,905) | [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 primarily of intercompany reinsurance balances and repurchase agreements.
[4] | Consists of intercompany deferred income taxes, reinsurance balances and repurchase agreements.

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