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Derivatives and Hedging Activities - Additional Information (Detail) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2021 USD ($) Derivative | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) Derivative
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Net gain (loss) on change in fair value | $ 6,263,000 | $ (5,553,000) |
Collateral posted with market value on liability positions with credit risk-related contingent features | $ 54,200,000 |  |
Interest Rate Swaps [Member] |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Number of interest rate swaps | Derivative | 122 |  | 112
Aggregate notional amount | $ 711,000,000.0 |  | $ 649,900,000
Net gain (loss) on change in fair value | 2,800,000 | (2,800,000) |
Income (loss) on derivative instrument not designated hedges | $ 1,900,000 | 2,600,000 |
Risk Participation in Agreements [Member] |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Number of interest rate swaps | Derivative | 13 |  | 12
Aggregate notional amount | $ 119,200,000 |  | $ 101,100,000
Risk Participation out Agreement [Member] |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Number of interest rate swaps | Derivative | 1 |  | 1
Aggregate notional amount | $ 10,000,000.0 |  | $ 10,000,000.0
Other Contract [Member] | Forward TBA Contracts [Member] |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Aggregate notional amount | 197,000,000.0 |  | $ 183,500,000
Net gain (loss) on change in fair value | $ 4,500,000 | $ (2,700,000) |

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998890-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details
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