Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Allowance for credit losses	$ 13,095	$ 9,913
Lease liability	7,858	8,363
Interest income on nonperforming loans	500	368
Compensation and benefits	11,580	10,972
Liabilities held at fair value	20	4
Deferred loan fees and costs	1,783	732
Other	1,097	1,110
Total	35,933	31,462
Deferred tax liabilities:
Prepaid pension	10,254	9,856
Right of use asset	7,270	7,790
Depreciation	3,735	4,688
Intangibles	1,266	1,128
Purchase accounting adjustments	5	274
Leases	2,425	2,472
Other	1,504	1,478
Total deferred tax liabilities	26,459	27,686
Net deferred tax asset at year-end	9,474	3,776	$ 6,849
Net deferred tax asset at beginning of year	3,776	6,849
Decrease (increase) in net deferred tax asset	5,698	(3,073)
CECL accounting standard adoption recorded through equity	586	0
Deferred tax expense	$ (6,284)	$ 3,073	$ 2,354