Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Summary Of Significant Accounting Policies [Line Items]
Core deposit intangibles amortization period, years	10 years
Net investment in LIHTCs	$ 14.7	$ 14.0
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years	3 years
Estimated useful life of intangibles, years	8 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful life of the asset, years	40 years
Estimated useful life of intangibles, years	13 years