Accumulated Other Comprehensive Income - Summary of Changes in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 01, 2015	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				$ 32,948
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax			$ (17)		$ 17
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	$ 0	$ 0	(17)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	90	0	0
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	8,976	0
Beginning balance	16,639	(21,546)	8,226
Other comprehensive income before reclassifications	(10,303)	29,683	(30,520)
Amounts reclassified from accumulated other comprehensive income	(385)	(474)	748
Net other comprehensive (loss) income	(10,688)	38,185	(29,772)
Ending balance	22,260	16,639	(21,546)
Unrealized holding gains (losses) on AFS
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				16,495
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	0	8,976
Beginning balance	16,495	(21,690)	8,065
Other comprehensive income before reclassifications	(6,117)	29,683	(30,503)
Amounts reclassified from accumulated other comprehensive income	(385)	(474)	748
Net other comprehensive (loss) income	(6,502)	38,185	(29,755)
Ending balance	9,993	16,495	(21,690)
Supplemental Employee Retirement Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				0
Beginning balance	0
Other comprehensive income before reclassifications	90
Amounts reclassified from accumulated other comprehensive income	0
Net other comprehensive (loss) income	90
Ending balance	90	0
Financial Liability Instruments, Fair Value Option [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income before reclassifications	(4,276)
Net other comprehensive (loss) income	(4,276)
Fair Value, Measurements, Recurring [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				16,309
Ending balance	12,033
Impairment loss on securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Comprehensive Income (Loss), after Adoption of New Accounting Principle				$ 144
Beginning balance	144	144	144
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Net other comprehensive (loss) income	0	0
Ending balance	$ 144	$ 144	$ 144