Fair Value of Financial Instruments - Reconciliation of Fair Value of Recurring Level 3 Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Limited liability investments, at fair value:
Beginning balance	$ 29,078
Purchases	(60)	$ (249)
Net realized gains	208	315
Ending balance	30,986
Real estate investments:
Beginning balance	10,662
Ending balance	10,662
Total assets	59,717		$ 65,520
Warrant liability:
Beginning balance	249
Ending balance - liabilities	216
Included in other comprehensive income (loss)	0	0
Significant Unobservable Inputs (Level 3)
Limited liability investments, at fair value:
Beginning balance	4,392	4,124
Purchases	0	75
Distributions received	(77)	(324)
Net realized gains	86	69
Change in fair value of limited liability investments, at fair value included in net (loss) income	12	116
Ending balance	4,413	4,060
Included in other comprehensive income (loss)	12	116
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0	0
Real estate investments:
Beginning balance	10,662	10,662
Change in fair value of real estate investments included in net (loss) income	0	0
Ending balance	10,662	10,662
Unrealized gains recognized on real estate investments held at end of period:	0	0
Total assets	15,075	14,722	$ 15,054
Warrant liability:
Beginning balance	249	0
Issuance of warrants	0	361
Change in fair value of warrant liability included in net (loss) income	(33)	(44)
Ending balance - liabilities	216	317
Included in net (loss) income	$ (33)	$ (44)