Summary of Significant Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Subsidiary
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Number of wholly-owned subsidiaries merged | Subsidiary	2
Maximum refinement period of fair values after closing date of an acquisition	1 year
Loan minimum balance included in the specific reserve analysis | $	$ 1
Tax Credit carry forward period	20 years
Federal NMTC Investment [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Period of tax credit earning	7 years
Low Income Housing Investments [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Period of tax credit earning	10 years
Commercial Loans [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Loss emergence period	18 months
Retail Loans [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Loss emergence period	12 months
Maximum [Member] | State NMTC Investment [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Period of tax credit earning	5 years
Minimum [Member] | State NMTC Investment [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Period of tax credit earning	3 years
Building [Member] | Maximum [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Estimated useful lives of the assets	39 years
Furniture, Fixtures and Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Estimated useful lives of the assets	10 years
Furniture, Fixtures and Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Estimated useful lives of the assets	3 years
Software [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Amortization expense charged off period	3 years
Core Systems [Member]
Summary Of Significant Accounting Policies And Recent Accounting Pronouncements [Line Items]
Amortization expense charged off period	7 years