Commitments and Contingencies - Summary of Contractual Amounts for Unfunded Commitments and Letters of Credit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Total amount	$ 8,827,108	$ 8,184,214
Percent of commercial real estate loans owner occupied	31.00%	36.00%
Unfunded Loan Commitment [Member]
Other Commitments [Line Items]
Loss Contingency Accrual	$ 9,000	$ 8,200
Standby letters of credit [Member]
Other Commitments [Line Items]
Total amount	175,778	390,161
Unsecured Letters Of Credit	5,850
Credit card guarantees [Member]
Other Commitments [Line Items]
Total amount	302,909	237,312
Commitments to extend credit [Member]
Other Commitments [Line Items]
Total amount	$ 8,348,421	$ 7,556,741
Loans Receivable [Member] | Credit Concentration Risk [Member] | Commercial Real Estate Portfolio Segment [Member]
Other Commitments [Line Items]
Concentration Risk, Percentage	45.00%	49.00%