Revenue Recognition - Contract Balances with Contract Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable	$ 476	$ 15
Costs and estimated earnings in excess of billings on uncompleted contracts	987	680
Other current assets	1,311	1,015
Billings on uncompleted contracts in excess of related costs	0	5
Other current liabilities	10,154	10,142
Contracts with Customers
Accounts receivable	476	15
Costs and estimated earnings in excess of billings on uncompleted contracts	987	680
Other current assets	0	70
Billings on uncompleted contracts in excess of related costs	0	5
Other current liabilities	$ 10,000	$ 10,000