Cash Deposits and Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance collateral deposits	$ 675	$ 1,233
Excess loss fund	521	943
Accumulated interest income	425	609
State collateral deposits	65	37
Materials and supplies	507	477
Total cash deposits and other assets	$ 2,193	$ 3,299