XML 63 R35.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Earnings Per Share (Tables) | 3 Months Ended
--- | ---
Mar. 31, 2012
Earnings Per Share [Abstract] |
Schedule Of Basic And Diluted Earnings Per Share |
|  | Three Months Ended March 31, |
$ in millions except share and per share amounts |  | 2012 |  |  | 2011 |
Net income (loss) |  | $ | 10 |  |  | $ | (1,274) |
Basic weighted average shares(1) |  |  | 193,489,424 |  |  |  | 199,972,759 |
Effect of common stock equivalents: |  |  |  |  |  |  |  |
Stock options |  |  | 1,105,550 |  |  |  | - |
Diluted weighted average shares |  |  | 194,594,974 |  |  |  | 199,972,759 |
Net income (loss) per common share: |  |  |  |  |  |  |  |
Basic |  | $ | 0.05 |  |  | $ | (6.37) |
Diluted |  | $ | 0.05 |  |  | $ | (6.37) |
(1) - Includes 5,219,053 and 5,228,926 of unvested restricted stock and units that receive nonforfeitable dividends or dividend equivalents for the three months ended March 31, 2012 and 2011, respectively.

X
- Definition Schedule of Basic and Diluted Earnings Per Share [Text Block] + References No definition available. + Details
Name: | mbi_ScheduleOfBasicAndDilutedEarningsPerShareTextBlock
Namespace Prefix: | mbi_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_EarningsPerShareAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration