Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gain on transfer of HTM securities to AFS, net of tax effect of $0, $0, $(5,367), $0 for each respective period presented	$ 0	$ 0	$ 8,976	$ 0
Beginning balance	8,472	(10,750)	(21,546)	8,226
Other comprehensive income before reclassifications	1,124	(4,800)	22,293	(23,687)
Amounts reclassified from accumulated other comprehensive loss	(113)	1,046	(240)	957
Net other comprehensive income (loss)	1,011	(3,754)	31,029	(22,730)
Ending balance	9,483	(14,504)	9,483	(14,504)
Unrealized holding gains (losses) on AFS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gain on transfer of HTM securities to AFS, net of tax effect of $0, $0, $(5,367), $0 for each respective period presented			8,976
Beginning balance	8,328	(10,780)	(21,690)	8,209
Other comprehensive income before reclassifications	1,124	(4,770)	22,293	(23,670)
Amounts reclassified from accumulated other comprehensive loss	(113)	1,046	(240)	957
Net other comprehensive income (loss)	1,011	(3,724)	31,029	(22,713)
Ending balance	9,339	(14,504)	9,339	(14,504)
Impairment loss on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	144		144
Other comprehensive income before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive loss	0		0
Net other comprehensive income (loss)	0		0
Ending balance	144		144
Unrealized gain on cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		30		17
Other comprehensive income before reclassifications		(30)		(17)
Amounts reclassified from accumulated other comprehensive loss		0		0
Net other comprehensive income (loss)		(30)		(17)
Ending balance		$ 0		$ 0