Business Segment, Geographic and Quarterly Financial Data - Operations by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Revenues	$ 4,912	$ 6,452	$ 8,948	$ 10,155	$ 15,827	$ 16,070	$ 11,847	$ 12,791	$ 30,467	$ 56,535	$ 45,166
Assets
Assets:	32,224				51,719				32,224	51,719
United States
Revenues:
Revenues									25,882	43,887	29,510
Assets
Assets:	23,460				36,784				23,460	36,784
Foreign
Revenues:
Revenues									4,585	12,648	$ 15,656
Assets
Assets:	$ 8,764				$ 14,935				$ 8,764	$ 14,935