Ownership Interests in and Advances to Partner Companies and Funds - Schedule of Results of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments in and Advances to Affiliates [Abstract]
Revenue	$ 40,070	$ 91,137	$ 234,049	$ 275,154
Gross profit	21,822	60,836	153,387	180,158
Net loss	$ (34,885)	$ (52,648)	$ (120,971)	$ (148,439)