Commitments and Contingent Liabilities - Commitments to Extend Credit, Guarantees and Various Letters of Credit Outstanding (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Lines of credit	$ 2,469,676	$ 1,894,030
Loans approved but not closed	504,623	258,778
Overdraft limits	149,519	153,572
Letters of credit	57,205	42,841
Contingent obligations and other guarantees	$ 81,551	$ 61,509