Other Comprehensive Income (Loss) - Components of Other Comprehensive Income (loss) Pre-Tax and After-Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Net unrealized gains (losses) on investments available for sale arising during the period, Pre-tax	$ 3,925	$ 6,020
Less: Amounts reclassified from accumulated other comprehensive income (loss), Pre-tax	63	(667)
Net current period other comprehensive income (loss), Pre-tax	3,988	5,353
Net unrealized gains (losses) on investments available for sale arising during the period, Tax	1,500	2,327
Less: Amounts reclassified from accumulated other comprehensive income (loss), Tax	24	(255)
Net current period other comprehensive income (loss), Tax	1,524	2,072
Net unrealized gains (losses) on investments available for sale arising during the period, After-tax	2,425	3,693
Less: Amounts reclassified from accumulated other comprehensive income (loss), After-tax	39	(412)
Net current period other comprehensive income (loss), After-tax	$ 2,464	$ 3,281

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Amount before tax, after reclassification adjustments of other comprehensive income (loss).

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Amount before tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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