Stockholders' Equity - Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance	$ 579,672	$ 549,464	$ 532,608
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act to Retained Earnings			2,073
Impact of adoption of Accounting Standard Update 2016-01	(875)
Total other comprehensive income (loss) , net of tax	(6,459)	2,945	(2,472)
Balance	618,997	579,672	549,464
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Balance	(3,982)	(15,649)	(5,522)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act to Retained Earnings			(1,325)
Other comprehensive income before reclassifications, net of tax	4,787	11,657	(10,127)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	485	10	1,325
Total other comprehensive income (loss) , net of tax	5,272	11,667	(8,802)
Balance	1,290	(3,982)	(15,649)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Balance	(5,863)	3,704	231
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act to Retained Earnings			50
Other comprehensive income before reclassifications, net of tax	(14,924)	(8,606)	3,351
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	3,266	(961)	72
Total other comprehensive income (loss) , net of tax	(11,658)	(9,567)	3,423
Balance	(17,521)	(5,863)	3,704
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance	(983)	(1,673)	(3,695)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act to Retained Earnings			(798)
Other comprehensive income before reclassifications, net of tax	(1,112)	661	2,484
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	211	29	336
Total other comprehensive income (loss) , net of tax	(901)	690	2,820
Balance	(1,884)	(983)	(1,673)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Balance	1,021	866
Impact of adoption of Accounting Standard Update 2016-01			779
Other comprehensive income before reclassifications, net of tax	828	155	87
Total other comprehensive income (loss) , net of tax	828	155	87
Balance	1,849	1,021	866
AOCI Attributable to Parent [Member]
Balance	(9,807)	(12,752)	(8,986)
Reclassification of the Income Tax Effects of the Tax Cuts and Jobs Act to Retained Earnings			(2,073)
Impact of adoption of Accounting Standard Update 2016-01	0		779
Other comprehensive income before reclassifications, net of tax	(10,421)	3,867	(4,205)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	3,962	(922)	1,733
Total other comprehensive income (loss) , net of tax	(6,459)	2,945	(2,472)
Balance	$ (16,266)	$ (9,807)	$ (12,752)