Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance collateral deposits	$ 714	$ 714
Excess loss fund	622	617
Accumulated interest income	489	449
State collateral deposits	36	31
Materials and supplies	493	488
Debt issuance costs	323	0
Other	288	84
Total other assets	$ 2,965	$ 2,383