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Impairment of Investment Securities - Pooled Trust Preferred Collateralized Debt Obligations (Detail) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2016 USD ($) Bank | Dec. 31, 2015 USD ($)
Impairment Of Investment Securities [Line Items] |  |
Securities available for sale, at fair value | $ 890,198 | $ 886,560
Unrealized Gain (Loss) | 11,405 | $ 16,477
Pooled Trust Preferred Collateralized Debt Obligations [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | 42,500 |
Securities available for sale, at fair value | 33,273 |
Unrealized Gain (Loss) | (9,227) |
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 | 1,291 |
Unrealized Gain (Loss) | $ (539) |
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 | 59.28% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL VII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 3,020 |
Securities available for sale, at fair value | 3,272 |
Unrealized Gain (Loss) | $ 252 |
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 | $ 2,020 |
Securities available for sale, at fair value | 1,705 |
Unrealized Gain (Loss) | $ (315) |
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 | $ 2,385 |
Securities available for sale, at fair value | 1,778 |
Unrealized Gain (Loss) | $ (607) |
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 | 9.82% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL X [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 1,644 |
Securities available for sale, at fair value | 1,779 |
Unrealized Gain (Loss) | $ 135 |
Debt Instrument, Credit Rating | Caa1/C |
Number of Banks (in banks) | Bank | 43 |
Deferrals and Defaults as a % of Current Collateral | 30.66% |
Excess Subordination as a % of Current Performing Collateral | 0.00% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL XII [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 5,735 |
Securities available for sale, at fair value | 4,324 |
Unrealized Gain (Loss) | $ (1,411) |
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 | $ 12,767 |
Securities available for sale, at fair value | 9,856 |
Unrealized Gain (Loss) | $ (2,911) |
Debt Instrument, Credit Rating | Ba3/C |
Number of Banks (in banks) | Bank | 56 |
Deferrals and Defaults as a % of Current Collateral | 12.11% |
Excess Subordination as a % of Current Performing Collateral | 42.17% |
Pooled Trust Preferred Collateralized Debt Obligations [Member] | Mezzanine [Member] | Pre TSL XIV [Member] |  |
Impairment Of Investment Securities [Line Items] |  |
Book Value | $ 12,889 |
Securities available for sale, at fair value | 8,969 |
Unrealized Gain (Loss) | $ (3,920) |
Debt Instrument, Credit Rating | B1/CC |
Number of Banks (in banks) | Bank | 56 |
Deferrals and Defaults as a % of Current Collateral | 19.72% |
Excess Subordination as a % of Current Performing Collateral | 49.72% |
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 | 299 |
Unrealized Gain (Loss) | $ 89 |
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 | 83.30% |

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