Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015 InterestPlans	Mar. 31, 2014
Loss Contingencies [Line Items]
Carried interest plans	2acta_NumberOfCarriedInterestPlans
Carried interest rate	0.15
Plan investment deployed amount approximately		$ 25.5
Maximum
Loss Contingencies [Line Items]
Plan investment deployed amount approximately	86.0

For investments which are quantified by principal amount, the principle balance held at close of period.

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

-Publisher FASB

-Name Accounting Standards Codification

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

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611133-123010

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant