Revenue Recognition - Contract Balances (Details) - USD ($)		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Receivables, which are included in accounts receivable - trade, net	$ 4,514,000	$ 1,973,000
Contract costs, net, which are included in other current assets	623,000	1,644,000
Payables, which are included in other current liabilities	3,139,000	1,295,000
Contract liabilities, which are included in other current liabilities	4,667,000	8,043,000	$ 0
Contract costs, net, which are included in other assets	3,740,000	4,268,000
Contract liabilities, which are included in other liabilities	27,983,000	$ 27,314,000
Commercial leasing contracts, receivable and payable term expectation		12 months
Contract liabilities estimated to be recognized over next twelve months		$ 8,043,000
Contract liabilities increase		2,707,000
Advance payments received from customer		15,551,000
Revenue recognized on contract liabilities	$ 9,738,000
Revenue recognized relating to performance obligations satisfied or partially satisfied in prior periods		$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation term		2 years