Notes Receivable (Percentage Of Gross Notes Receivable Outstanding By FICO Score At Origination) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of gross notes receivable outstanding	100.00%	100.00%
No Score [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of gross notes receivable outstanding	1.00%	1.00%
Less Than 600 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of gross notes receivable outstanding	3.00%	3.00%
601-700 [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of gross notes receivable outstanding	38.00%	37.00%
700+ [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of gross notes receivable outstanding	58.00%	59.00%