Preferred and Common Units Under LLC Structure (Narrative) (Details)	9 Months Ended
	Sep. 30, 2020 item / shares item $ / shares	Dec. 31, 2019 $ / shares
Class of Stock [Line Items]
Liquidation preference, per share | $ / shares	$ 100	$ 100
Series A Preferred Units [Member]
Class of Stock [Line Items]
Spread over LIBOR	0.25%
Interest rate measurement period	1 year
Preferred stock, dividend payment rate	10%
Liquidation preference, per share | $ / shares	$ 100
Number of voting rights | item / shares	0
Threshold of number of consecutive quarters without paid preferred return for appointment of managers | item	4
Number of managers that can be appointed after threshold for period of unpaid preferred returns reached | item	2