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Guarantees, Commitments and Contingencies - Additional Information (Detail) (USD $) | 0 Months Ended | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | ---
Sep. 27, 2007 Complaints | Jun. 30, 2014 | Jun. 30, 2013 | Jun. 30, 2014 Complaints | Dec. 31, 2013
Long-term Purchase Commitment [Line Items] |  |  |  |  |
Credit losses associated with derivative contracts |  | $ 0 | $ 0 |  |
Outstanding commitments to purchase securities |  | 600,000 |  | 600,000 | 3,000,000
Outstanding commitments to sell securities |  | $ 0 |  | $ 0 | $ 0
Number of allegations asserted separate counts | 18 |  |  |  |
Number of pending allegations |  |  |  | 2 |
Unjust Enrichment [Member] |  |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |  |
Number of pending allegations |  |  |  | 1 |
Breach of Contract [Member] |  |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |  |
Number of pending allegations |  |  |  | 1 |

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- Details
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