Investments (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 5,853	$ 7,304
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair values	5,853	7,304
U.S. Treasury notes [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	16	47
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair values	16	47
U.S. Treasury bills [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0	1,400
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair values	0	1,400
Money market mutual funds [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	5,837	5,856
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair values	5,837	5,856
Other short-term interest-bearing securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	0	1
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair values	$ 0	$ 1

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) 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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