Credit Losses, Financial Assets and Other Instruments (Credit Risk Classification) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investing Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	$ 64,354
2016	0
2017	971
2018	0
2019	6,041
2020	239
Total	71,605	$ 73,523
Investing Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	64,354
2016	0
2017	971
2018	0
2019	0
2020	239
Total	65,564
Investing Receivables \| Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	0
2016	0
2017	0
2018	0
2019	6,041
2020	0
Total	6,041
Tenant Notes Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	97
2016	179
2017	0
2018	1,192
2019	1,967
2020	2,146
Total	5,581
Tenant Notes Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	0
2016	14
2017	0
2018	1,028
2019	84
2020	343
Total	1,469
Tenant Notes Receivables \| Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	97
2016	165
2017	0
2018	164
2019	1,883
2020	1,803
Total	4,112
Sales-Type Lease Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2015 and Earlier	0
2016	0
2017	0
2018	0
2019	0
2020	6,573
Total	$ 6,573

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Amount of financing receivable originated four years prior to current fiscal year.

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Amount of financing receivable originated in current fiscal year.

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Amount of financing receivable originated in fiscal year prior to current fiscal year.

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Amount of financing receivable originated three years prior to current fiscal year.

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Amount of financing receivable originated two years prior to current fiscal year.

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Amount, before allowance for credit loss, of financing receivable.

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