| Loans - Loans (Parenthetical) (Detail) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019 | 
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| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Total gross loans receivable | $ 4,543,636 | $ 4,610,147 | 
| Consumer | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Total gross loans receivable | 12,090 | 13,670 | 
| Consumer | Home equity line of credit | ||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||
| Total gross loans receivable | $ 7,500 | $ 8,200 | 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount, before allowance for credit loss, of financing receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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