Financial Instruments Financial Insttruments (Schedule of Cash, Cash Equivalents and Marketable Securities) (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash				$ 1,507	$ 1,892
Cash and cash equivalents		$ 4,411	$ 4,411	3,254	4,605	$ 5,300
Marketable securities				2,974	1,362
Proceeds from Sale of Available-for-sale Securities		$ 205	$ 465
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash				1,507	1,892
Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Cash				0	0
Fair Value, Inputs, Level 2 [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[1]			4,721	4,075
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[1]			1,747	2,713
Fair Value, Inputs, Level 2 [Member] | Marketable Securities [Member]
Cash and Cash Equivalents [Line Items]
Certificate of deposits / time deposits	[1]			$ 2,974	$ 1,362

[1] Represents held-to-maturity investments reported at amortized cost.