Comprehensive Income (Loss), Net of Tax - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Before-Tax Amount
Other comprehensive income (loss)	$ 7,446	$ 9,993	$ (6,657)
Tax Expense (Benefit)
Other comprehensive income (loss)	(1,905)	(2,540)	1,692
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss) before reclassifications	5,187	6,776	(5,287)
Reclassification from AOCI, current period	354	677	322
Other Comprehensive Income (Loss)	5,541	7,453	(4,965)
Unrealized Gains and Losses on Available for Sale Securities
Before-Tax Amount
OCI, before reclassifications	7,129	5,580	(2,839)
Reclassification from AOCI, current period	37
Tax Expense (Benefit)
Other comprehensive income (loss) before reclassifications	1,823	1,418	(723)
Reclassification from AOCI, current period	(9)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss) before reclassifications	5,306	4,162	(2,116)
Reclassification from AOCI, current period	28	0	0
Other Comprehensive Income (Loss)	5,334	4,162	(2,116)
Net Unrealized Gains on Cash Flow Swap
Before-Tax Amount
OCI, before reclassifications	651
Tax Expense (Benefit)
Other comprehensive income (loss) before reclassifications	166
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss) before reclassifications	485	0
Reclassification from AOCI, current period		0
Other Comprehensive Income (Loss)	485	0
Net Actuarial Gain (Loss)
Before-Tax Amount
OCI, before reclassifications	(337)	3,505	(3,798)
Tax Expense (Benefit)
Other comprehensive income (loss) before reclassifications	(86)	891	(965)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss) before reclassifications	(251)	2,614	(2,833)
Reclassification from AOCI, current period	169	510	242
Other Comprehensive Income (Loss)	(82)	3,124	(2,591)
Net Prior Service (Cost) Credit
Before-Tax Amount
OCI, before reclassifications	(472)		(453)
Tax Expense (Benefit)
Other comprehensive income (loss) before reclassifications	(119)		(115)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other comprehensive income (loss) before reclassifications	(353)	0	(338)
Reclassification from AOCI, current period	157	167	80
Other Comprehensive Income (Loss)	(196)	167	(258)
Net Retirement Plan Gains and Losses
Before-Tax Amount
Reclassification from AOCI, current period	227	684	325
Tax Expense (Benefit)
Reclassification from AOCI, current period	(58)	(174)	(83)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Reclassification from AOCI, current period	169	510	242
Accretion of Net Prior Service (Cost) Credit
Before-Tax Amount
Reclassification from AOCI, current period	211	224	108
Tax Expense (Benefit)
Reclassification from AOCI, current period	(54)	(57)	(28)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Reclassification from AOCI, current period	$ 157	$ 167	$ 80