Acquisitions Martin Currie Acquisition (Details) £ in Thousands, AUD in Thousands, $ in Thousands	3 Months Ended				12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 AUD	Jun. 30, 2016 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 GBP (£)	Mar. 31, 2016 USD ($)	Jun. 30, 2017 AUD	Jun. 30, 2017 GBP (£)	Jun. 30, 2017 USD ($)		Oct. 21, 2015 USD ($)	Oct. 01, 2014 USD ($)	May 30, 2014 USD ($)
QS Investors [Domain]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current										$ 0
Business Combination, Contingent Consideration, Liability					$ 4,841		$ 13,749			3,583				$ 13,370
Payments to Acquire Businesses, Gross				$ 11,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High										23,400
Contingent consideration fair value adjustments	$ (1,258)
RARE Infrastructure, Ltd [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current					7,791					0
Assets Under Management												$ 6,800,000
Business Combination, Contingent Consideration, Liability					17,444		27,145			2,128		$ 25,000
Payments to Acquire Businesses, Gross		AUD 296,000	$ 213,739
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High								AUD 106,000		81,426	[1]
Contingent consideration fair value adjustments	(15,316)
Martin Currie [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current										12,480
Business Combination, Contingent Consideration, Liability					12,018		41,222			12,480			$ 75,211
Payments to Acquire Businesses, Gross						£ 125,000	$ 202,577
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High									£ 325,000	$ 423,075	[1]
Change in Input Assumptions [Member] | QS Investors [Domain]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	(1,300)				(2,500)
Change in Input Assumptions [Member] | RARE Infrastructure, Ltd [Member]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	(15,250)				(10,000)
Change in Input Assumptions [Member] | Martin Currie [Member]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	0				(25,000)
Other changes in Fair Value [Member] | QS Investors [Domain]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	42				179
Other changes in Fair Value [Member] | RARE Infrastructure, Ltd [Member]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	(66)				299
Other changes in Fair Value [Member] | Martin Currie [Member]
Business Acquisition [Line Items]
Contingent consideration fair value adjustments	$ 462				$ (4,204)

[1] Using the applicable exchange rate as of June 30, 2017, for amounts denominated in currencies other than the U.S. dollar.