Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 19
Document Period End Date	Dec. 31, 2020
Interest Rate Caps Sold
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	$ 6,000	$ 5,900
Purchase [Member]
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	2,900	2,700
Interest Rate Cap [Member]
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	8,871	8,625
Interest Rate Cap [Member] \| Subsidiary Issuers
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	3,100	3,200
Interest Rate Swap [Member]
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	1,950	1,500
Currency Swap [Member]
Schedule of Cost-method Investments [Line Items] (Deprecated 2018-01-31)
Derivative, Notional Amount	$ 1,386	$ 1,518

The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is YYYY-MM-DD.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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The estimated net amount of unrealized gains or losses on interest rate cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121549185&loc=d3e80748-113994

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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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