Stock-Based Compensation (Details 4) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Restricted Stock Units and Restricted Stock
Unit and Shares Activity:
Number of Awards - Nonvested - Beginning balance	3,261,562
Number of Awards - Granted - Annual	946,774
Number of Awards - Granted - Other	38,193
Number of Awards - Vested	(1,035,090)
Number of Awards - Forfeited	(26,212)
Number of Awards - Nonvested - Ending balance	3,185,227
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures
Weighted Average Grant Date Fair Value - Nonvested - Beginning balance	$ 85.17
Weighted Average Grant Date Fair Value - Granted - Annual	$ 101.57
Weighted Average Grant Date Fair Value - Granted - Other	$ 109.82
Weighted Average Grant Date Fair Value - Vested	$ 79.83
Weighted Average Grant Date Fair Value - Forfeited	$ 89.96
Weighted Average Grant Date Fair Value - Nonvested - Ending balance	$ 92.04
Vesting period	3 years
Weighted average life of remaining vesting period	27 months
Fair value that vested	$ 106	$ 162
Compensation expense yet to be recognized	112
Tax benefit realized from vesting	40	84
Performance Shares
Unit and Shares Activity:
Number of Awards - Nonvested - Beginning balance	1,089,084
Number of Awards - Granted - Annual	342,131
Number of Awards - Vested	(506,725)
Number of Awards - Performance Change	(29,559)
Number of Awards - Forfeited	(20,845)
Number of Awards - Nonvested - Ending balance	874,086
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures
Weighted Average Grant Date Fair Value - Nonvested - Beginning balance	$ 79.27
Weighted Average Grant Date Fair Value - Granted - Annual	$ 96.23
Weighted Average Grant Date Fair Value - Vested	$ 75.16
Weighted Average Grant Date Fair Value - Performance Change	$ 87.43
Weighted Average Grant Date Fair Value - Forfeited	$ 91.72
Weighted Average Grant Date Fair Value - Nonvested - Ending balance	$ 87.72
Performance criteria, number of key factors	3
Weighted average life of remaining vesting period	10 months
Share-based compensation arrangement by share-based payment award, award vesting or performance period	3 years
Fair value that vested	52	0
Compensation expense yet to be recognized	27
Tax benefit realized from vesting	$ 16	$ 0
Performance Shares \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures
Number of shares to be delivered based on percent of each performance share granted upon satisfaction of performance conditions	200.00%
Vesting period	3 years
Performance Shares \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures
Number of shares to be delivered based on percent of each performance share granted upon satisfaction of performance conditions	0.00%
Vesting period	1 year

Percentage of vesting of share-based compensation awards.

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- Definition

The number of shares issuable under a share-based award plan pertaining to grants made during the period on other than stock option plans.

+ References

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The weighted average fair value at grant for nonvested share-based awards issued during the period on other than stock option plans, other than annual and performance shares.

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The increase or decrease in the number of equity-based payment instruments, excluding stock (or unit) options, attributable to performance change during the reporting period.

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The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans, increased or decreased for performance change during the reporting period.

+ References

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- Definition

Description of award terms as to the number of key factors comprising the performance criteria for vesting of an award.

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- Definition

Adjustment to additional paid in capital related to the net effect of excess tax benefits and tax deficiencies associated with an equity-based compensation plan other than an employee stock ownership plan (ESOP).

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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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