Investment Securities - Proceeds from Sale, Gross Gains (Losses) Realized on Sales, Maturities and Other-Than-Temporary Impairment Charges Related to Securities Available for Sale (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from Sale of Available-for-sale Securities	$ 55,744	$ 0
Sales Transactions:
Gross gains	304	0
Gross losses	(276)	0
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	28	0
Maturities and impairment
Gross Gains	0	125
Gross Losses	0	0
Other Than Temporary Impairment	0	0
Gain Losses Maturities And Impairment	0	125
Net gains and impairment	$ 28	$ 125