Debt - Schedule of Fair Value of Senior Notes (Detail) - Senior notes - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Fair Value	$ 6,173	$ 6,277
Book Value	$ 5,480	$ 5,588

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant