Commitments and Contingent Liabilities - Commitments to Extend Credit, Guarantees and Various Letters of Credit Outstanding (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Lines of credit	$ 2,497,734	$ 2,510,011
Loans approved but not closed	470,736	381,180
Overdraft limits	153,374	154,322
Letters of credit	53,136	53,788
Contingent obligations and other guarantees	$ 199,066	$ 126,984