Summary of Fund Interests and Other Similar Deferred Compensation Arrangements (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Prepaid Compensation Asset, Balance January 1, 2012	$ 17,782
Prepaid Compensation Asset, Granted	64,658
Prepaid Compensation Asset, Settled
Prepaid Compensation asset, Forfeited	(1,607)
Prepaid Compensation Asset, Amortization (including grants of awards to retirement-eligible recipients)	(24,508)
Prepaid Compensation Asset, Change in fair value of underlying investments
Prepaid Compensation Asset, Adjustment for estimated forfeitures
Other	101
Balance, September 30, 2012	56,426
Compensation liability, Balance January 1, 2012	29,900
Compensation liability, Granted	64,658
Compensation liability, Settled	(8,640)
Compensation liability, Forfeited	(1,706)
Compensation liability, Amortization (including grants of awards to retirement-eligible recipients)
Compensation liability, Change in fair value of underlying investments	4,639
Compensation liability, Adjustment for estimated forfeitures	2,202
Compensation liability, Other
Compensation liability, Balance, September 30, 2012	$ 91,053

Derivative Liability Adjustment To Forfeiture

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- Definition

Derivative liability, amortization.

+ References

No definition available.

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- Definition

Derivative liability, change in fair value.

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No definition available.

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- Definition

Derivative liability, foreign currency translation and other adjustments.

+ References

No definition available.

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- Definition

Derivative liability forfeited.

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No definition available.

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- Definition

Derivative liability, granted.

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No definition available.

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- Definition

Derivative Liability, Vested

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No definition available.

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- Definition

Prepaid compensation asset.

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No definition available.

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- Definition

Prepaid Compensation Asset Adjustment To Forfeiture

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No definition available.

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Prepaid compensation asset, change in fair value.

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No definition available.

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Prepaid compensation asset, foreign currency translation and other adjustments.

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No definition available.

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Prepaid compensation asset forfeited.

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No definition available.

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Prepaid compensation asset, granted.

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No definition available.

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Prepaid compensation asset, settled.

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No definition available.

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- Definition

The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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- Definition

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-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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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 44C

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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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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