Revenue Recognition - Contract Balances with Contract Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts receivable, net	$ 552	$ 1,079
Deferred revenue	15	21
Contract liabilities	9,271	9,755
Costs and estimated earnings in excess of billings on uncompleted contracts	0	0
Other current assets	413	729
Other current liabilities	42	83
Contracts with Customers
Accounts receivable, net	552	1,079
Accrued liabilities	200	432
Deferred revenue	15	21
Contract liabilities	$ 9,271	$ 9,755