Acquisitions RARE Acquisition - Fair Value Assumptions (Details) - RARE Infrastructure, Ltd [Member]	3 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Fund management contracts [Member]
Business Acquisition, Contingent Consideration [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		12 years
Fair Value, Inputs, Level 3 [Member] \| Asset Management Contracts
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Inputs, Discount Rate		16.50%
Fair Value Inputs, Long-term AUM Growth Rate		7.00%
Fair Value Inputs, Attrition Rate		8.00%
Fair Value, Inputs, Level 3 [Member] \| Trade Names
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, High End of Range	10.00%
Fair Value Input, Projected Cash Flow Growth Rate, Average	7.00%
Fair Value Inputs, Discount Rate	16.50%
Fair Value, Inputs, Level 3 [Member] \| Fund management contracts [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, High End of Range	10.00%
Fair Value Input, Projected Cash Flow Growth Rate, Average	7.00%
Fair Value Inputs, Discount Rate	16.50%
Performance Fees [Member] \| Fair Value, Inputs, Level 3 [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, Average		3.00%
Earn-out Payments [Member] \| Fair Value, Inputs, Level 3 [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Inputs, Discount Rate		1.90%
Assets Under Management [Member] \| Fair Value, Inputs, Level 3 [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fair Value Input, Projected Cash Flow Growth Rate, Average		7.00%
Fair Value Inputs, Discount Rate		6.50%
Fair Value Assumptions, Weighted Average Volatility Rate		20.00%

Percentage of assumed growth rate in projected cash flows, used as an input to measure fair value, average

No definition available.

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- Definition

Percentage of assumed growth rate in projected cash flows, used as an input to measure fair value, high end of range

+ References

No definition available.

+ Details

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- Definition

Amount used to represent the attrition when calculating the fair value of amortizable asset management contracts

+ References

No definition available.

+ Details

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- Definition

Percentage of assumed long-term growth in AUM, used as an input to measure fair value.

+ References

No definition available.

+ Details

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- Definition

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Weighted average expected volatility of stock price.

+ 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 (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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