Comprehensive Income (Loss) - Components of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Before Tax Amount
Other Comprehensive Income (Loss)	$ 12,387	$ 13,871	$ (4,203)
Tax Benefit (Expense)
Other Comprehensive Income (Loss)	(3,238)	(3,785)	757
Net of Tax Amount
Other comprehensive income (loss) before classifications	10,021
Reclassification adjustment for securities gains included in net income	(872)
Other comprehensive income (loss)	9,149	10,086	(3,446)
Unrealized Gains (Losses)  on Available- for-Sale Securities
Before Tax Amount
Unrealized holding gains on securities available for sale arising during the period	14,049
Reclassification adjustment for securities gains included in net income	(1,213)
Other Comprehensive Income (Loss)	12,836	14,763	(4,241)
Tax Benefit (Expense)
Other Comprehensive Income (Loss) before Reclassifications, Tax	3,711
Reclassification adjustment for securities gains included in net income	341
Other Comprehensive Income (Loss)	(3,370)	(4,045)	734
Net of Tax Amount
Other comprehensive income (loss) before classifications	10,338
Reclassification adjustment for securities gains included in net income	(872)
Other comprehensive income (loss)	9,466	10,718	(3,507)
Unrealized losses on derivatives
Before Tax Amount
Other Comprehensive Income (Loss)	(413)	(828)	9
Tax Benefit (Expense)
Other Comprehensive Income (Loss)	121	242	32
Net of Tax Amount
Other comprehensive income (loss) before classifications	(292)
Reclassification adjustment for securities gains included in net income	0
Other comprehensive income (loss)	(292)	(586)	41
Change in pension liability, net
Before Tax Amount
Other Comprehensive Income (Loss)	(36)	(64)	29
Tax Benefit (Expense)
Other Comprehensive Income (Loss)	11	18	(9)
Net of Tax Amount
Other comprehensive income (loss) before classifications	(25)
Reclassification adjustment for securities gains included in net income	0
Other comprehensive income (loss)	$ (25)	$ (46)	$ 20