Investments (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Short-term investments:
Equity investment securities	$ 25	$ 25
Available-for-sale investment securities	1,361	1,760
Held-to-maturity investment securities	826	1,065
Time Deposits	506	500
Total short-term investments	2,718	3,350
Long-term investments:
Equity and cost method investments	73	74
Held-to-maturity investment securities	6	6
Total long-term investments	79	80
Restricted investments	$ 427	$ 423

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Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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