Notes Receivable and Current Expected Credit Losses (Changes in Allowance for Credit Loss) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			$ 0
Unrealized credit loss provision	$ (117,000)	$ 0	260,000	$ 0
Ending balance	$ 3,085,000		3,085,000
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			$ 2,825,000