Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Loan commitments	$ 3,743,000,000	$ 3,566,000,000
Fixed rate loan commitment	3,478,000,000
Floating rate loan commitment	265,300,000
Standby letters of credit	$ 100,200,000	319,000,000.0
Loan commitments floating rate, minimum	1.00%
Loan commitments floating rate, maximum	16.00%
Allowance for unfunded loan commitments	$ 2,200,000	2,500,000
Extended credit	2,200,000	15,500,000
Credit extensions with collateral	$ 7,800,000	$ 7,800,000
Class B Restricted Shares [Member] | Visa [Member]
Loss Contingencies [Line Items]
Restricted stock conversion ratio	1.6298
Investment owned, balance, shares | shares	56,210
Investment owned, at cost	$ 0