Debt Investments (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Proceeds from sales of available-for-sale securities			$ 339	$ 742
Gross realized gains			41	84
Available-for-sale Securities, Gross Realized Losses			(8)	(25)
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	$ 22		22
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	23		23
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	618		618
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	650		650
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	709		709
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	720		720
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost	510		510
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	540		540
Debt Securities, Available-for-sale, Amortized Cost	1,859		1,859		$ 1,495
Debt Securities, Available-for-sale	1,933		1,933		1,634
Equity Securities, Net Unrealized Gain (Loss)	6	$ 1		$ 1
Equity Securities without Readily Determinable Fair Value, Amount	226		226		215
Equity Securities, FV-NI, Current	$ 25		$ 25		$ 40

Equity Securities, Net Unrealized Gain (Loss)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

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