Fair Value Measurements - Summary of Changes in Fair Value of Company's Level 3 Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value Measurements [Line Items]
Beginning Balance	$ 133,100	$ 163,798	$ 136,219
Net Unrealized/Realized Gains (Losses) Included In Revenue-Other	16,118	(3,416)	8,652
Purchases/Acquisitions	8,599	43,482	34,302
Sales/Dispositions	(42,670)	(69,413)	(11,985)
Foreign Currency Translation Adjustments	954	(1,351)	(3,390)
Ending Balance	116,101	133,100	163,798
Equities [Member]
Fair Value Measurements [Line Items]
Beginning Balance	211	316	305
Net Unrealized/Realized Gains (Losses) Included In Revenue-Other	5	72	6
Purchases/Acquisitions		25	14
Sales/Dispositions	(30)	(195)
Foreign Currency Translation Adjustments	4	(7)	(9)
Ending Balance	190	211	316
Alternative investments [Member]
Fair Value Measurements [Line Items]
Beginning Balance	10,171
Net Unrealized/Realized Gains (Losses) Included In Revenue-Other	130	(169)
Purchases/Acquisitions		10,340
Sales/Dispositions	(6,844)
Ending Balance	3,457	10,171
Equity funds [Member]
Fair Value Measurements [Line Items]
Purchases/Acquisitions	10
Ending Balance	10
Private equity [Member]
Fair Value Measurements [Line Items]
Beginning Balance	122,718	163,482	135,914
Net Unrealized/Realized Gains (Losses) Included In Revenue-Other	15,983	(3,319)	8,646
Purchases/Acquisitions	8,589	33,117	34,288
Sales/Dispositions	(35,796)	(69,218)	(11,985)
Foreign Currency Translation Adjustments	950	(1,344)	(3,381)
Ending Balance	$ 112,444	$ 122,718	$ 163,482

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Foreign Currency Translation Adjustments

+ References

No definition available.

+ Details

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- Definition

Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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- Definition

Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-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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