Financial Instruments (Schedule of Cash, Cash Equivalents and Marketable Securities) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash		$ 1,630	$ 1,938
Cash and cash equivalents		4,166	5,300
Marketable securities		623	906
Proceeds from sale of available-for-sale securities		260
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash		1,630	1,938
Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash		0	0
Fair Value, Inputs, Level 1 [Member]
Cash and Cash Equivalents [Line Items]
Money market funds		412	550
U.S. Treasury securities	[1]	529	788
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Money market funds		412	550
U.S. Treasury securities	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Money market funds		0	0
U.S. Treasury securities	[1]	529	788
Fair Value, Inputs, Level 2 [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[2]	2,218	2,930
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[2]	2,124	2,812
Fair Value, Inputs, Level 2 [Member] | Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[2]	$ 94	$ 118

[1] Available-for-sale securities are reported at estimated fair value with unrealized gains and losses reported as component of accumulated other comprehensive loss. Proceeds from the sale of available-for-sale securities were $260 in the three months ended March 31, 2016.

[2] Held-to-maturity investments are reported at amortized cost.