Financial Instruments (Cash, Cash Equivalents and Marketable Securities) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash		$ 1,938	$ 2,181
Cash, cash equivalents and marketable securities		5,300	6,910
Marketable securities		906	124
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash		1,938	2,181
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		550	1,436
U.S. Treasury securities	[1]	788	0
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Money market funds		550	1,436
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]	788	0
Fair Value, Inputs, Level 2 [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposit / time deposits	[2]	2,930	3,417
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposit / time deposits	[2]	2,812	3,293
Fair Value, Inputs, Level 2 [Member] | Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposit / time deposits	[2]	$ 118	$ 124

[1] Available-for-sale securities are reported at estimated fair value with unrealized gains and losses reported as component of accumulated other comprehensive loss.

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