Premises and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019
Property Plant And Equipment Capitalized Interest Costs [Abstract]
Operating lease liabilities	$ 467,320		$ 488,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesMember		us-gaap:OtherLiabilitiesMember
Period of noncancelable operating lease in years	21 years
Net lease expense		$ 111,000