Comprehensive Income (Loss), Net of Tax - Reclassification Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ 47,075	$ 45,305	$ 39,855
Provision for Income Taxes	(9,600)	(9,026)	(10,529)
Net of tax	(677)	(322)	(691)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss on Securities Transactions, Net	0	0	(448)
Total before tax	0	0	(448)
Provision for Income Taxes	0	0	111
Net of tax	0	0	(337)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	(224)	(108)	11
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	(684)	(325)	(411)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for Income Taxes	231	111	46
Net of tax	(677)	(322)	(354)
Actuarial gains/(losses)	$ (908)	$ (433)	$ (400)