Interest-bearing Time Deposits in Banks and Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016 USD ($) Investment	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Interest Bearing Time Deposits In Banks And Securities [Line Items]
INTEREST-BEARING TIME DEPOSITS IN BANKS	$ 2,427,000	$ 9,170,000	$ 3,495,000
Time deposits with balances greater than $250,000, FDIC insured limit	0	489,000	489,000
Time deposits balances, FDIC insured limit	250,000	250,000	250,000
Held-to-maturity securities	$ 146,000	310,000	$ 278,000
Number of investment positions | Investment	30
Securities pledged as collateral	$ 1,600,768,000
Sales of investment securities available-for-sale	553,000	1,129,000
Gross realized gains from security sales	7,000	5,000
Gross realized losses from security sales or calls	$ 5,000	$ 0
Minimum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits, maturity period, years	1 year
Maximum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits, maturity period, years	3 years