Commitments and Contingencies - Commitments and Contingent Liabilities Outstanding (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Commitments to extend credit
Home equity lines of credit	$ 5,713,950	$ 5,693,045
Commercial real estate loans to be sold	321,654	324,943
Other commercial real estate	4,523,995	4,998,631
Residential real estate loans to be sold	146,491	233,257
Other residential real estate	982,216	924,211
Commercial and other	21,884,664	22,145,057
Standby letters of credit	2,177,405	2,151,595
Commercial letters of credit	53,732	31,981
Financial guarantees and indemnification contracts	4,453,722	4,211,797
Commitments to sell real estate loans	$ 862,061	$ 1,367,523