Commitments and Contingent Liabilities - Commitments to Extend Credit, Guarantees and Various Letters of Credit Outstanding (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Lines of credit	$ 2,510,011	$ 2,469,676
Loans approved but not closed	381,180	504,623
Overdraft limits	154,322	149,519
Letters of credit	53,788	57,205
Contingent obligations and other guarantees	$ 126,984	$ 81,551