Notes Receivable and Current Expected Credit Losses (Changes in Allowance for Credit Loss) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 0
Provision for unrealized credit losses	377,000	$ 0
Ending balance	3,202,000
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 2,825,000