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Variable Interest Entities - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
9 Months Ended | ||||||
|---|---|---|---|---|---|---|---|
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Sep. 30, 2012
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Sep. 30, 2012
Affordable Housing Real Estate Joint Ventures
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Dec. 31, 2011
Affordable Housing Real Estate Joint Ventures
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Sep. 30, 2012
Real Estate Joint Ventures
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Dec. 31, 2011
Real Estate Joint Ventures
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Sep. 30, 2012
Fixed-Rate Senior Mortgage Loan Commitments
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Dec. 31, 2011
Fixed-Rate Senior Mortgage Loan Commitments
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| Variable Interest Entity [Line Items] | |||||||
| Number of ventures invested by company | 27 | 28 | 8 | 11 | |||
| Mortgage loans, carrying value | $ 16.4 | $ 1.7 | $ 7.0 | ||||
| Losses realizable if tax credits received were recaptured | $ 12.8 | $ 13.2 | |||||
| Maximum exposure to loss, required compliance period, years | 15 years |