Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

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- Definition

Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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- Definition

This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments.

+ References

No definition available.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

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- Definition

Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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Cash, Cash Equivalents, and Marketable Securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total cash and cash equivalents	$ 8,766	$ 9,558
Restricted Cash	148	124
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	8,914	9,682	$ 8,357	$ 8,185
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	924	1,028
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities	3,708	2,881
Investment Type [Member] \| Fair Value, Estimate Not Practicable, Carrying (Reported) Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash, time deposits and money market funds	7,842	8,530
US Government [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	44	0
Marketable securities	1,116	966
US Government Agencies [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	50	300
Marketable securities	265	384
Foreign Government Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	556	703
Marketable securities	1,517	660
Corporate debt [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash and cash equivalents	274	25
Marketable securities	680	848
Other Debt Obligations [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities	$ 130	$ 23