Securities - Sales of Securities Available for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 0	$ 2,028	$ 223,987	$ 2,028
Gross realized gains	0	3	228	3
Gross realized losses	0	(1)	0	(1)
Tax (expense) benefit of securities gains/losses	$ 0	$ (1)	$ (80)	$ (1)