Related Party (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Notes Payable, Related Parties, Noncurrent	$ 251		$ 550
Deemed contribution from partners	$ 0	$ 4
ETO [Member]
Related Party Transaction [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.03%

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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The amount for notes payable (written promise to pay), payable to related parties, which are due after one year (or one business cycle).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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Total contributions made by each class of partners (i.e., general, limited and preferred partners).

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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