| Organization and Basis of Presentation - Additional Information (Detail) $ in Millions | 3 Months Ended | |
|---|---|---|
| Jan. 01, 2020  Segment | Mar. 31, 2020  USD ($) | |
| Organization Consolidation And Presentation Of Financial Statements [Abstract] | ||
| Number of loan segments | Segment | 4 | |
| Increase to beginning balance of allowance for credit losses | $ 17.4 | |
| Decrease to beginning balance of allowance for off balance sheet items | (0.3) | |
| After-tax charge to retained earnings | $ 12.2 | 
| X | ||||||||||
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- Definition Number of loan segment. No definition available. 
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- Definition Amount of the cumulative effect on retained earnings net of related income tax effect. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of increase (decrease) in allowance for credit loss on financing receivable. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of expense (reversal of expense) for expected credit loss on off-balance sheet commitment, from change in methodology. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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