Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock-Based Compensation Arrangement by Stock-based Payment Award
Stock-based compensation expense (benefit)	$ 26	$ (5)	$ 8	$ 47
Income tax benefit (expense) for stock-based compensation arrangements	9	(3)	2	17
Tax benefit realized from exercise of stock-based compensation arrangements	30	21	33	38
Stock appreciation rights
Stock-Based Compensation Arrangement by Stock-based Payment Award
Stock-based compensation expense (benefit)	13	(15)	(5)	24
Performance share awards
Stock-Based Compensation Arrangement by Stock-based Payment Award
Stock-based compensation expense (benefit)	7	2	4	10
Market stock units
Stock-Based Compensation Arrangement by Stock-based Payment Award
Stock-based compensation expense (benefit)	5	4	8	8
Other stock-based awards
Stock-Based Compensation Arrangement by Stock-based Payment Award
Stock-based compensation expense (benefit)	$ 1	$ 4	$ 1	$ 5

The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

No definition available.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (j)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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