Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2020
Derivative [Line Items]
Notional amount	$ 14,526,000,000	$ 12,480,000,000
Additional amount in excess of posted collateral required in case of breached agreements	200,000	300,000
Subject to master netting arrangements:
Derivative [Line Items]
Notional amount	$ 7,627,000,000	6,221,000,000
Interest rate contracts
Derivative [Line Items]
Maximum length of time hedged in interest rate cash flow hedge	3 years 9 months 18 days
Period to reclassification of cash flow hedge gain loss	12 months
Derivative loss to be reclassified within twelve months	$ 9,800,000
Derivative loss to be reclassified within twelve months, net of tax	7,600,000
Hedge ineffectiveness	0
Amount of gain (loss) reclassified from AOCI into net income	0	0
Interest rate contracts | Subject to master netting arrangements:
Derivative [Line Items]
Termination of derivative contract, notional amount			$ 225,000,000
Notional amount	$ 2,080,000,000	1,430,000,000
Interest rate lock commitments | Minimum
Derivative [Line Items]
Lock in period for interest rates	30 days
Interest rate lock commitments | Maximum
Derivative [Line Items]
Lock in period for interest rates	270 days
Credit risk contracts
Derivative [Line Items]
Notional amount	$ 247,800,000
Maximum exposure under credit risk agreement assuming customer default	200,000	600,000
Credit risk derivatives, purchased at fair value	100,000	200,000
Credit risk derivatives, sold at fair value	$ 200,000	$ 600,000
Credit risk contracts | Minimum
Derivative [Line Items]
Risk participation agreements, term	7 months
Credit risk contracts | Maximum
Derivative [Line Items]
Risk participation agreements, term	19 years