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% |