Derivative Financial Instruments - Schedule of Effect of Derivative Instruments on the Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income on Derivative	$ 8,261	$ (543)
Gain (Loss) Reclassified from AOCI into Income	5,153	596
Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	5,154	665	$ (154)
Interest rate contracts \| Interest income/(expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income on Derivative	8,261	(543)	5,145
Gain (Loss) Reclassified from AOCI into Income	5,153	596	(150)
Interest rate contracts \| Interest income/(expense) \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	8,211
Gain (Loss) Recognized in Income on Related Hedged Items	(8,250)
Interest rate contracts \| Other income/(expense) \| Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	(551)	(174)	(7)
Fixed-rate debt \| Interest income/(expense) \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	7,238	12,577	7,662
Gain (Loss) Recognized in Income on Related Hedged Items	(7,283)	(12,587)	(7,634)
Fixed-rate investment securities \| Interest income/(expense) \| Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	973
Gain (Loss) Recognized in Income on Related Hedged Items	(967)
Mortgage contracts \| Mortgage banking revenue \| Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	5,692	789	(189)
Foreign currency contracts \| Other income/(expense) \| Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$ 13	$ 50	$ 42

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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