Investments - Amortized Cost, Gross Unrealized Gains and Losses, Fair Values of Investments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Debt Securities
Amortized Cost	$ 440	$ 444
Gross Unrealized Gains	5	7
Gross Unrealized Losses	0	0
Fair Value	445	451
Asset-backed securities
Debt Securities
Amortized Cost	25	24
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	25	24
Corporate bonds
Debt Securities
Amortized Cost	121	126
Gross Unrealized Gains	2	2
Gross Unrealized Losses	0	0
Fair Value	123	128
U.S. government agencies and government- sponsored agencies
Debt Securities
Amortized Cost	23	27
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	23	28
U.S. treasuries
Debt Securities
Amortized Cost	256	261
Gross Unrealized Gains	3	4
Gross Unrealized Losses	0	0
Fair Value	259	265
Certificate of deposits
Debt Securities
Amortized Cost	9	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	9	0
Other debt securities
Debt Securities
Amortized Cost	6	6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 6	$ 6

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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Amount, before tax, of unrealized loss 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).

+ References

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

+ References

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-Publisher FASB
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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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-Publisher FASB
-Name Accounting Standards Codification
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