Revenues Revenues (Contract Assets and Liabilities) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Movement in Contract Assets and Liabilities [Roll Forward]
Unbilled revenue, beginning balance	$ 964
Contract liability, beginning balance	5,328
Unbilled revenue, ending balance	3,937
Contract liability, ending balance	4,561
Increase in unbilled revenue	2,973
Increase in accrued customer advances	$ (767)