Investments - Summary of Cost and Carrying Value of Equity and Trading Debt Securities (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Total trading debt securities, Cost	$ 1,194	$ 1,926
Equity securities at FVTNI, Cost	1,451	2,055
Total trading debt, Carrying Value	1,186	1,964
Equity securities at FVTNI, Carrying Value	1,738	2,317
Corporate Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	703	1,591
Total trading debt, Carrying Value	701	1,641
Government Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	365	203
Total trading debt, Carrying Value	363	210
Asset/Mortgage-Backed Debt [Member]
Schedule of Investments [Line Items]
Total trading debt securities, Cost	126	132
Total trading debt, Carrying Value	122	113
Equity Securities/Mutual Funds [Member]
Schedule of Investments [Line Items]
Equity securities at FVTNI, Cost	1,451	2,055
Equity securities at FVTNI, Carrying Value	$ 1,738	$ 2,317

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562

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-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124260329&loc=d3e26610-111562

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