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Common and Preferred Stock (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Class of Stock [Line Items] |  |  |
Fair value of warrants | $ 6 | $ 33 |
Remaining amount available under repurchase program | $ 250 | $ 88 | $ 94
Treasury stock shares acquired | 43,000,000 | 16,600,000 | 39,900,000
Shares repurchased under share repurchase program, average price per share | $ 7.55 | $ 6.37 | $ 7.6
Preferred stock shares issued | 0 | 0 |
Preferred stock shares outstanding | 0 | 0 |
Preferred Stock Par Or Stated Value Per Share | $ 1 | $ 1 |
Preferred Stock [Member] | MBIA Insurance Corporation [Member] |  |  |
Class of Stock [Line Items] |  |  |
Shares repurchased under share repurchase program, average price per share | $ 10,900 |  |
Preferred stock shares issued | 2,759 |  |
Preferred stock repurchased during period shares | 1,444 |  |
Preferred stock, carrying value issued and outstanding | $ 28 |  |
Face value of repurchased preferred stock | 10.90% |  |
Preferred Stock Par Or Stated Value Per Share | $ 1,000 |  |
Preferred stock liquidation preference | $ 100,000 |  |
Dividend rate on preferred stock determined rate | LIBOR plus 200 basis points |  |
2014 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | $ 200 |  |
Stock repurchase program cancelled amount | 61 |  |
July 29, 2015 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | 100 |  |
October 28, 2015 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | 100 |  |
2016 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | 100 |  |
Stock repurchase program cancelled amount | 13 |  |
June 27, 2017 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | 250 |  |
November 3, 2017 Repurchase Authorization [Member] |  |  |
Class of Stock [Line Items] |  |  |
Authorized repurchase of common stock, value | 250 |  |
Remaining amount available under repurchase program | $ 250 |  |
Unaffiliated Investors [Member] | MBIA Insurance Corporation [Member] |  |  |
Class of Stock [Line Items] |  |  |
Preferred stock shares outstanding | 1,315 |  |
Long-Term Incentive Plan [Member] |  |  |
Class of Stock [Line Items] |  |  |
Treasury stock shares acquired | 490,557 | 419,806 |
Warrant [Member] | HighBridge |  |  |
Class of Stock [Line Items] |  |  |
Warrants outstanding | 9,940,000 |  |
Warrant exercise price | $ 9.59 |  |
Warrant Term | 5 years |  |
Grossup Warrant [Member] | HighBridge |  |  |
Class of Stock [Line Items] |  |  |
Warrants outstanding | 1,910,000 |  |
Warrant exercise price | $ 9.59 |  |
Warrant Term | 5 years |  |

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