Investments in Privately Held Companies - Minority Investment Entities (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) company	Jun. 30, 2017 USD ($) company	Jun. 30, 2018 USD ($) company	Jun. 30, 2017 USD ($) company
Minority investment entities
Minority investments not consolidated accounted for under equity method | company	7	7	7	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	$ 8,993,000	$ 5,908,000	$ 16,349,000	$ 11,363,000
Gross profit	1,702,000	4,277,000	1,737,000	7,999,000
Operating income (loss)	1,871,000	(794,000)	708,000	(1,631,000)
Net income (loss)	694,000	(818,000)	(737,000)	(2,523,000)
Minority investment entities
Entity income (loss) excluding impairment	$ 307,000	$ (188,000)	$ (27,000)	$ (1,100,000)