Comprehensive Income - Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ 309,398	$ 276,609	$ 301,728	$ 269,584
Other comprehensive income or loss before reclassifications	2,039	1,744	5,918	3,824
Amounts reclassified from accumulated other comprehensive income	97	176	163	339
Other Comprehensive Income	2,136	1,920	6,081	4,163
Stockholders' equity, ending balance	317,687	284,649	317,687	284,649
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(2,412)	(11,567)	(6,357)	(13,810)
Stockholders' equity, ending balance	(276)	(9,647)	(276)	(9,647)
Unrealized Gains and Losses on Available for Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	4,563	(1,617)	465	(3,697)
Other comprehensive income or loss before reclassifications	2,021	1,744		3,824
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other Comprehensive Income	2,021	1,744	6,119	3,824
Stockholders' equity, ending balance	6,584	127	6,584	127
Unrealized Loss on Cash Flow Swap
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(219)	0	0	0
Other comprehensive income or loss before reclassifications	18	0	(201)	0
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other Comprehensive Income	18	0	(201)	0
Stockholders' equity, ending balance	(201)	0	(201)	0
Net Actuarial Gain (Loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(5,820)	(8,850)	(5,847)	(8,971)
Other comprehensive income or loss before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	58	133	85	254
Other Comprehensive Income	58	133	85	254
Stockholders' equity, ending balance	(5,762)	(8,717)	(5,762)	(8,717)
Net Priot Service (Cost) Credit
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(936)	(1,100)	(975)	(1,142)
Other comprehensive income or loss before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	39	43	78	85
Other Comprehensive Income	39	43	78	85
Stockholders' equity, ending balance	$ (897)	$ (1,057)	$ (897)	$ (1,057)