Summary of Non-vested stock and Stock Unit Awards (Detail) (USD $)	12 Months Ended
Dec. 31, 2012 Y
Restricted Stock And Stock Units
WEIGHTED AVERAGE REMAINING VESTING TERM (YEARS)
Nonvested at beginning of year	2.4
Nonvested at end of year	2.0
Stock and Stock Unit Awards
NUMBER
Beginning Balance	2,809,067
Granted	988,421
Vested	(487,980)
Forfeited	(173,012)
Ending Balance	3,136,496
WEIGHTED AVERAGE GRANT-DATE FAIR VALUE PER UNIT
Nonvested at beginning of year	52.33
Granted	43.72
Vested	52.38
Forfeited	49.13
Nonvested at end of year	49.20

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Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Weighted Average Remaining Vesting Term, Beginning Balance

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Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Weighted Average Remaining Vesting Term, Ending Balance

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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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-Name Accounting Standards Codification

-Topic 718

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- Definition

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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- Definition

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

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-Name Accounting Standards Codification

-Topic 718

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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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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