Investments in Privately Held Companies - Minority Investment Entities (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) company	Mar. 31, 2017 USD ($)
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net loss	$ (334,000)	$ (933,000)
Minority investment entities
Minority investments not consolidated accounted for under equity method | company	7
Seven Minority Investments
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net revenue	$ 7,356,000	5,455,000
Gross profit	35,000	3,722,000
Operating loss	(1,163,000)	(837,000)
Net loss	$ (1,430,000)	$ (1,705,000)
Minority investment entities
Minority investments not consolidated accounted for under equity method | company	7