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Impairment of Investment Securities - Pooled Trust Preferred Collateralized Debt Obligations (Detail) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2016 USD ($) Bank | Dec. 31, 2015 USD ($)
Impairment Of Investment Securities [Line Items] |  |
Securities available for sale, at fair value | $ 855,333 | $ 886,560
Unrealized Gain (Loss) | 9,761 | $ 16,477
Pooled Trust Preferred Collateralized Debt Obligations [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | 42,750 |
Securities available for sale, at fair value | 33,723 |
Unrealized Gain (Loss) | (9,027) |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL IV [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | 1,830 |
Securities available for sale, at fair value | 1,301 |
Unrealized Gain (Loss) | $ (529) |
Debt Instrument, Credit Rating | B1/BB |
Number of Banks (in banks) | Bank | 6 |
Deferrals and Defaults as a % of Current Collateral | 18.05% |
Excess Subordination as a % of Current Performing Collateral | 58.51% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL VII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 3,061 |
Securities available for sale, at fair value | 3,324 |
Unrealized Gain (Loss) | $ 263 |
Debt Instrument, Credit Rating | Ca/- |
Number of Banks (in banks) | Bank | 14 |
Deferrals and Defaults as a % of Current Collateral | 49.68% |
Excess Subordination as a % of Current Performing Collateral | 0.00% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL VIII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 2,042 |
Securities available for sale, at fair value | 1,691 |
Unrealized Gain (Loss) | $ (351) |
Debt Instrument, Credit Rating | C/C |
Number of Banks (in banks) | Bank | 28 |
Deferrals and Defaults as a % of Current Collateral | 53.00% |
Excess Subordination as a % of Current Performing Collateral | 0.00% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL IX [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 2,394 |
Securities available for sale, at fair value | 1,797 |
Unrealized Gain (Loss) | $ (597) |
Debt Instrument, Credit Rating | B1/C |
Number of Banks (in banks) | Bank | 38 |
Deferrals and Defaults as a % of Current Collateral | 29.80% |
Excess Subordination as a % of Current Performing Collateral | 9.73% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL X [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 1,675 |
Securities available for sale, at fair value | 1,817 |
Unrealized Gain (Loss) | $ 142 |
Debt Instrument, Credit Rating | Caa1/C |
Number of Banks (in banks) | Bank | 43 |
Deferrals and Defaults as a % of Current Collateral | 32.22% |
Excess Subordination as a % of Current Performing Collateral | 2.20% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL XII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 5,786 |
Securities available for sale, at fair value | 4,442 |
Unrealized Gain (Loss) | $ (1,344) |
Debt Instrument, Credit Rating | B3/C |
Number of Banks (in banks) | Bank | 66 |
Deferrals and Defaults as a % of Current Collateral | 22.03% |
Excess Subordination as a % of Current Performing Collateral | 0.00% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL XIII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 12,828 |
Securities available for sale, at fair value | 9,971 |
Unrealized Gain (Loss) | $ (2,857) |
Debt Instrument, Credit Rating | Ba3/C |
Number of Banks (in banks) | Bank | 56 |
Deferrals and Defaults as a % of Current Collateral | 11.34% |
Excess Subordination as a % of Current Performing Collateral | 47.86% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL XIV [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 12,924 |
Securities available for sale, at fair value | 9,075 |
Unrealized Gain (Loss) | $ (3,849) |
Debt Instrument, Credit Rating | B1/CC |
Number of Banks (in banks) | Bank | 56 |
Deferrals and Defaults as a % of Current Collateral | 15.21% |
Excess Subordination as a % of Current Performing Collateral | 38.08% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | MMCap I [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 210 |
Securities available for sale, at fair value | 305 |
Unrealized Gain (Loss) | $ 95 |
Debt Instrument, Credit Rating | Ca/C |
Number of Banks (in banks) | Bank | 8 |
Deferrals and Defaults as a % of Current Collateral | 58.11% |
Excess Subordination as a % of Current Performing Collateral | 81.96% |

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