Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Useful Lives for Principal Classes of Assets (Detail)

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Summary of Significant Accounting Policies - Useful Lives for Principal Classes of Assets (Detail)
12 Months Ended
Dec. 31, 2018
Leasehold improvements  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life Term of lease or useful life, whichever is shorter
Software  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life 3 years
Minimum | Buildings and improvements  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life 10 years
Minimum | Furniture and equipment  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life 3 years
Maximum | Buildings and improvements  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life 30 years
Maximum | Furniture and equipment  
Property, Plant and Equipment [Line Items]  
Premises and equipment useful life 10 years