Fair Value Measurements (Details 4) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gain on Sale of Investments	$ 10,609	$ 8,669	$ 7,478
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(9,828)	0	0
Proceeds from Issuance of Warrants	0	(10,239)	(8,589)
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants	424	324	821
Equity Warrants Transfers to Available For Sale Securities	$ (119)	(113)	78
Warrants Not Settleable in Cash, Fair Value Disclosure		$ 3,434	$ 4,793	$ 5,161