Commitments and Contingencies Commitments and Contingencies related to Acquisitions (Details) £ in Thousands, AUD in Thousands, $ in Thousands		3 Months Ended			9 Months Ended	12 Months Ended
		Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 AUD	Dec. 31, 2016 GBP (£)	Dec. 31, 2016 USD ($)		Aug. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	[2]	Oct. 21, 2015 USD ($)	May 05, 2015 USD ($)	Mar. 31, 2015 USD ($)	Oct. 01, 2014 USD ($)	May 30, 2014 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability						$ 84,585			$ 35,484							$ 110,784
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability						27,457			2,000
Business Combination, Contingent Consideration, Liability, Current									2,494
Business Combination, Contingent Consideration, Liability, Noncurrent									32,990
Business Acquisition, Preacquisition Contingency, Amount of Settlement						22,765			6,587
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[1]								530,399
RARE Infrastructure, Ltd [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability						27,145			16,415					$ 25,000		0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability	[2]													$ 25,000
Business Combination, Contingent Consideration, Liability, Current									0
Business Combination, Contingent Consideration, Liability, Noncurrent									16,415
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					$ (10,730)
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High							AUD 106,000		76,451	[1]
Martin Currie [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability						41,222			11,775							70,114	$ 75,211
Business Combination, Contingent Consideration, Liability, Current									0
Business Combination, Contingent Consideration, Liability, Noncurrent									11,775
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(29,447)
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High								£ 325,000	400,413	[1]
PK Investments [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[1]								2,494
QS Investors [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability						13,749			4,800							13,553		$ 13,370
Business Combination, Contingent Consideration, Liability, Current									0
Business Combination, Contingent Consideration, Liability, Noncurrent									4,800
Business Acquisition, Preacquisition Contingency, Amount of Settlement											$ (6,587)
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					8,949
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High									23,400
Fauchier [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability						0			0							27,117
Business Combination, Contingent Consideration, Liability, Current									0
Business Combination, Contingent Consideration, Liability, Noncurrent									0
Business Acquisition, Preacquisition Contingency, Amount of Settlement											$ (6,587)				$ (22,765)
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[1]								24,641
Other Affiliates [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration, Liability	[3]					2,469			2,494							$ 0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability	[3]								2,000			$ 2,457
Business Combination, Contingent Consideration, Liability, Current	[3]								2,494
Business Combination, Contingent Consideration, Liability, Noncurrent	[3]								0
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[3]								5,494
Other changes in Fair Value [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(5,014)	2,484
Other changes in Fair Value [Member] | RARE Infrastructure, Ltd [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(730)	2,145
Other changes in Fair Value [Member] | Martin Currie [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(4,447)	(531)
Other changes in Fair Value [Member] | QS Investors [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					138	196
Other changes in Fair Value [Member] | Fauchier [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					0	662
Other changes in Fair Value [Member] | Other Affiliates [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[3]				25	12
Change in Input Assumptions [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(39,500)	(33,375)
Change in Input Assumptions [Member] | RARE Infrastructure, Ltd [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		$ (3,000)	$ (7,000)		(10,000)
Change in Input Assumptions [Member] | Martin Currie [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		$ (7,000)		$ (18,000)	(25,000)	(28,361)
Change in Input Assumptions [Member] | QS Investors [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(2,500)
Change in Input Assumptions [Member] | Fauchier [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability						$ (5,014)
Change in Input Assumptions [Member] | Other Affiliates [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	[3]				$ (2,000)
Contingent payment due on fourth anniversary of acquisition [Member] | QS Investors [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High									$ 20,000
Contingent payment due on fourth anniversary of acquisition [Member] | Fauchier [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High | £								£ 20,000

[1] Using the applicable exchange rate as of December 31, 2016, for amounts denominated in currencies other than the U.S. dollar.

[2] Using the applicable exchange rate on the date of acquisition for amounts denominated in currencies other than the U.S. dollar.

[3] Includes amounts related to the acquisition of Financial Guard on August 17, 2016 and PK Investments on December 31, 2015.