Commitments and Contingencies - Commitments and Contingent Liabilities Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Commitments to extend credit
Home equity lines of credit	$ 8,167,368	$ 8,261,560
Commercial real estate loans to be sold	338,569	348,701
Other commercial real estate	6,224,142	5,776,116
Residential real estate loans to be sold	237,683	31,208
Other residential real estate	406,667	505,121
Commercial and other	33,670,583	32,625,840
Standby letters of credit	2,333,434	2,376,644
Commercial letters of credit	72,053	65,066
Financial guarantees and indemnification contracts	4,209,726	4,022,432
Commitments to sell real estate loans	$ 948,190	$ 533,458