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Derivative Financial Instruments - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | $ 1,452,000,000 |  |  |  | $ 665,500,000 |  |  |  | $ 1,452,000,000 | $ 665,500,000 |
Percentage of periodic changes in fair value qualifies for hedge accounting treatment | 100.00% |  |  |  |  |  |  |  | 100.00% |  |
Reclassified interest income (expense) | $ 161,079,000 | $ 145,573,000 | $ 145,671,000 | $ 143,771,000 | 148,899,000 | $ 153,096,000 | $ 155,230,000 | $ 147,048,000 | $ 596,094,000 | 604,273,000 | $ 537,602,000
Amount Reclassified from AOCI | Interest Income |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Reclassified interest income (expense) |  |  |  |  |  |  |  |  | 6,100,000 |  |
Amount Reclassified from AOCI | interest expense |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Reclassified interest income (expense) |  |  |  |  |  |  |  |  | (1,800,000) |  |
Fixed Interest Swap |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 379,000,000.0 |  |  |  | 130,500,000 |  |  |  | 379,000,000.0 | 130,500,000 |
Variable Interest Rate Swap, Available-for-sale Investment Securities |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 347,500,000 |  |  |  |  |  |  |  | 347,500,000 |  |
Variable Interest Rate Swap, Borrowings |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 325,000,000.0 |  |  |  | 25,000,000.0 |  |  |  | 325,000,000.0 | 25,000,000.0 |
Variable Interest Rate Collars and Floors |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 400,000,000.0 |  |  |  |  |  |  |  | 400,000,000.0 |  |
Variable Interest Rate Collar |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts |  |  |  |  | 510,000,000.0 |  |  |  |  | 510,000,000.0 |
Interest Rate Lock Commitments |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 224,700,000 |  |  |  | 65,700,000 |  |  |  | 224,700,000 | 65,700,000 |
Forward Commitments |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 261,000,000.0 |  |  |  | 101,600,000 |  |  |  | 261,000,000.0 | 101,600,000 |
Offsetting Counter Party Derivative Instrument |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 2,008,000,000.000 |  |  |  | 1,298,000,000 |  |  |  | 2,008,000,000.000 | 1,298,000,000 |
Customer Derivative Instrument |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | 2,008,000,000.000 |  |  |  | 1,298,000,000 |  |  |  | 2,008,000,000.000 | 1,298,000,000 |
Foreign Currency Forward Contract | Foreign currency contracts |  |  |  |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |  |
Notional amounts | $ 9,900,000 |  |  |  | $ 8,200,000 |  |  |  | $ 9,900,000 | $ 8,200,000 |

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