Credit Losses, Financial Assets and Other Instruments (Credit Risk Classification) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investing Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	$ 65,884
2017	994
2018	0
2019	6,041
2020	992
Total	73,911	$ 71,605
Investing Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	65,884
2017	994
2018	0
2019	0
2020	992
Total	67,870
Investing Receivables \| Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	0
2017	0
2018	0
2019	6,041
2020	0
Total	6,041
Tenant Notes Receivables
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	97
2017	157
2018	1,153
2019	1,870
2020	2,151
Total	5,428
Tenant Notes Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	0
2017	7
2018	997
2019	80
2020	326
Total	1,410
Tenant Notes Receivables \| Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	97
2017	150
2018	156
2019	1,790
2020	1,825
Total	4,018
Sales-Type Lease Receivables \| Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2016 and Earlier	0
2017	0
2018	0
2019	0
2020	6,507
Total	$ 6,507

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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 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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