Investments - Fair Values by Contractual Maturity (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$ 5,629	$ 17,424
Maturing after one year through three years	2,304	3,356
Maturing after three years through five years	119	5,168
Maturing after five years through ten years	0	885
Mortgage- and asset-backed securities	182	1,891
Total available-for-sale investments	$ 8,234	$ 28,724

Available-For Sale Securities, Debt Maturities, After One Through Three Years, Fair Value

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Available-For-Sale Securities, Debt Maturities, After Three Through Five Years, Fair Value

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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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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