Investment Securities - Realized Gains and Losses on Sales of Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]
Gross gains, Sales transactions	$ 103	$ 1	$ 103	$ 3,382
Gross gains, Maturities and other securities transactions	0	8	8	657
Gross losses, Maturities and other securities transactions	0	0	(9)	(31)
Gains (losses) on Maturities and other securities transactions, net	0	8	(1)	626
Total gains on securities transactions, net	$ 103	$ 9	$ 102	$ 4,008