Summary of Significant Accounting Policies - Narrative (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($) segment location
Property, Plant and Equipment [Line Items]
Number of client-focused reportable segment | segment	2
Lower Limit
Property, Plant and Equipment [Line Items]
Days contractually past due for interest and principal and the loan is not well-secured and in the process of collection	90 days
Upper Limit
Property, Plant and Equipment [Line Items]
Number of days past due for disclosure purposes to be categorized as a current	29 days
Buildings | Upper Limit
Property, Plant and Equipment [Line Items]
Charge for depreciation, range of life	30 years
Equipment | Lower Limit
Property, Plant and Equipment [Line Items]
Charge for depreciation, range of life	3 years
Equipment | Upper Limit
Property, Plant and Equipment [Line Items]
Charge for depreciation, range of life	10 years
Computer Software
Property, Plant and Equipment [Line Items]
Software, useful life	15 years
Computer Software | Lower Limit
Property, Plant and Equipment [Line Items]
Software, useful life	3 years
Computer Software | Upper Limit
Property, Plant and Equipment [Line Items]
Software, useful life	10 years
WEALTH MANAGEMENT
Property, Plant and Equipment [Line Items]
Minimum assets requirement to be managed | $	$ 200,000,000
Services provided by business units, states | location	19