Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Bank Properties and Equipment (Detail)	3 Months Ended
	Mar. 31, 2017
Buildings [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	40 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	Lesser of the useful life or the remaining lease term, including renewals, if applicable
Computer Software [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Minimum [Member] | Furniture, Fixtures and Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Maximum [Member] | Furniture, Fixtures and Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated Useful Life	10 years