Acquisitions RARE Acquisition (Details) AUD in Thousands, $ in Thousands		3 Months Ended				9 Months Ended		12 Months Ended
		Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 AUD	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 AUD	Dec. 31, 2016 USD ($)		Oct. 21, 2015 USD ($)	Mar. 31, 2015 USD ($)
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability								$ 27,457		$ 2,000
Line of Credit Facility, Fair Value of Amount Outstanding								40,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[1]									530,399
Business Combination, Contingent Consideration, Liability								84,585		35,484			$ 110,784
Business Combination, Contingent Consideration, Liability, Current										2,494
RARE Infrastructure, Ltd [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability	[2]											$ 25,000
Assets Under Management												$ 6,800,000
Noncontrolling Interest, Ownership Percentage by Parent												75.00%
Payments to Acquire Businesses, Gross				AUD 296,000	$ 213,739
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High									AUD 106,000	76,451	[1]
Business Combination, Contingent Consideration, Liability								27,145		16,415		$ 25,000	$ 0
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability						$ (10,730)
Business Combination, Contingent Consideration, Liability, Current										$ 0
Revenues							$ 8,376
RARE Management Team [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners												15.00%
Outside Investors
Business Acquisition [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners												10.00%
RARE Infrastructure, Ltd [Member]
Business Acquisition [Line Items]
Goodwill and Intangible Asset Impairment		$ 18,000
Change in Input Assumptions [Member]
Business Acquisition [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 [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		$ (3,000)	$ (7,000)			(10,000)
Other changes in Fair Value [Member]
Business Acquisition [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 [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability						$ (730)		$ 2,145

[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.