Change in Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 724,345	$ 687,336	$ 580,471
Other comprehensive income before reclassifications	(6,723)	2,889	(6,610)
Less: Amounts reclassified from accumulated other comprehensive loss	(519)	(1,764)	(1,703)
Net current-period other comprehensive loss	(7,242)	1,125	(8,313)
Less: Reclassification due to the adoption of ASU No. 2018-02		(1,660)
Ending Balance	820,920	724,345	687,336
Net change in investment securities available for sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(7,842)	(8,194)	(1,887)
Other comprehensive income before reclassifications	(6,695)	3,073	(4,838)
Less: Amounts reclassified from accumulated other comprehensive loss	(16)	(1,280)	(1,469)
Net current-period other comprehensive loss	(6,711)	1,793	(6,307)
Less: Reclassification due to the adoption of ASU No. 2018-02		(1,441)
Ending Balance	(14,553)	(7,842)	(8,194)
Net change in investment securities held to maturity
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	1,223	1,392	1,795
Other comprehensive income before reclassifications	6	0	0
Less: Amounts reclassified from accumulated other comprehensive loss	(450)	(394)	(403)
Net current-period other comprehensive loss	(444)	(394)	(403)
Less: Reclassification due to the adoption of ASU No. 2018-02		225
Ending Balance	779	1,223	1,392
Net change in defined benefit plan
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	865	957	788
Other comprehensive income before reclassifications	22	0	0
Less: Amounts reclassified from accumulated other comprehensive loss	(53)	(90)	169
Net current-period other comprehensive loss	(31)	(90)	169
Less: Reclassification due to the adoption of ASU No. 2018-02		(2)
Ending Balance	834	865	957
Net change in fair value of derivatives used for cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(2,398)	(1,772)	0
Other comprehensive income before reclassifications	(56)	(184)	(1,772)
Less: Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current-period other comprehensive loss	(56)	(184)	(1,772)
Less: Reclassification due to the adoption of ASU No. 2018-02		(442)
Ending Balance	(2,454)	(2,398)	(1,772)
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(8,152)	(7,617)	696
Less: Reclassification due to the adoption of ASU No. 2018-02	(1,700)
Ending Balance	$ (15,394)	$ (8,152)	$ (7,617)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings

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