Income Taxes - Summary of Temporary Differences in Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Unearned revenue	$ 5,633	$ 3,741
Basis difference in pension plan liability	452	0
Total deferred tax assets	6,085	3,741
Property, plant and equipment	16,314	17,030
§1031 tax exchanges	26,499	26,638
Deferred credits	1,853	748
Real estate acquired through foreclosure	142	142
Other	5	10
Total deferred tax liabilities	44,813	44,568
Deferred taxes payable	$ (38,728)	$ (40,827)