Financial Instruments - Debt and Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Financial Instruments:
Debt securities - noncurrent, Adjusted Cost	$ 7		$ 7		$ 5
Debt securities - noncurrent, Gross Unrealized Gains	3		3		3
Debt securities - noncurrent, Fair Value	10		10		8
Available-for-sale equity investments, Adjusted Cost	1		1		3
Available-for-sale equity investments, Gross Unrealized Gains	5		5		5
Available-for-sale equity investments, Gross Unrealized Losses	0		0		0
Available-for-sale equity investments, Fair Value	6		6		$ 7
Sales of debt and available-for-sale equity investments
Proceeds	0	$ 1	5	$ 149
Gross realized gains (before taxes)	0	0	1	0
Gross realized losses (before taxes)		0	2	37
Unrealized holding gains/(losses) on available-for-sale debt and marketable equity securities
Net unrealized gains/(losses) arising during the period	2	1	2	(22)
Net unrealized (gains)/losses reclassified to net income	0	0	1	23
Writedowns included in net income for the period	$ 0	$ 0	$ 0	$ 0
Maximum contractual maturities of substantially all available-for-sale debt securities			1 year

This describes the maximum time frame of the contract terms of the entity's available-for-sale debt securities.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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This item represents the cost of equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature more than one year from the balance sheet date or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Equity securities categorized neither as held-to-maturity nor trading which are intended be sold more than one year from the balance sheet date or operating cycle, if longer.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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-Publisher FASB
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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized loss realized upon the write-down of available-for-sale securities.

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-Publisher FASB
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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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