Interest-bearing Time Deposits in Banks and Securities - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014 Investment	Mar. 31, 2013	Dec. 31, 2013
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interest-bearing time deposits in banks	$ 30,026,000	$ 45,172,000	$ 31,917,000
Time deposits with balances greater than $100,000	27,351,000		29,002,000
Time deposits balances	100,000		100,000
Held to maturity securities	582,000	903,000	684,000
Number of investment positions	278
Securities pledged as collateral	1,329,068,000
Sales of investment securities available-for-sale	904,000	5,227,000
Gross realized gains from security sales and calls	1,000	223,000
Gross realized losses from security sales and calls	$ 5,000	$ 1,000
Minimum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interesting-bearing time deposits, maturity period, years	One
Maximum [Member]
Interest Bearing Time Deposits In Banks And Securities [Line Items]
Interesting-bearing time deposits, maturity period, years	Two