|
Cash, Cash Equivalents and Marketable Securities Available-for-Sale (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
Mar. 31, 2015
|
Dec. 31, 2014
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|---|---|---|
| Cash, Cash Equivalents, and Short-term Investments [Abstract] | ||
| Money market funds, at carrying value | $ 1,281 | $ 2,251 |