Revenue Recognition - Contract Balances with Contract Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable, net	$ 274	$ 476
Costs and estimated earnings in excess of billings on uncompleted contracts	1,199	987
Other current assets	1,091	1,311
Billings on uncompleted contracts in excess of related costs	5	0
Other current liabilities	10,095	10,154
Contracts with Customers
Accounts receivable, net	274	476
Costs and estimated earnings in excess of billings on uncompleted contracts	1,199	987
Billings on uncompleted contracts in excess of related costs	5	0
Other current liabilities	$ 10,000	$ 10,000