Cash Deposits and Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance collateral deposits	$ 709	$ 1,233
Excess loss fund	620	943
Accumulated interest income	332	609
State collateral deposits	33	37
Materials and supplies	493	477
Total	$ 2,187	$ 3,299