Revenue from Contracts with Customers - Contract Balances (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract assets	$ 986,000	$ 2,362,000
Deferred revenue and customer advances	4,286,000	6,034,000
Deferred revenue, included in other long-term liabilities	904,000	$ 578,000
Revenue recognized from amounts included in deferred revenue	4,100,000
Revenues recognized from satisfied in previous period	0
Capitalized contract costs	2,100,000
Impairment	$ 0