Subsequent Event (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Oct. 21, 2015
RARE Infrastructure, Ltd [Member]
Subsequent Event [Line Items]
Goodwill and Intangible Asset Impairment			$ 18,000
RARE Infrastructure, Ltd [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Change in Assets Under Management	$ 1,500,000
Goodwill and Intangible Asset Impairment		$ 34,000
RARE Infrastructure, Ltd [Member] | Trade Names | Subsequent Event [Member]
Subsequent Event [Line Items]
Goodwill and Intangible Asset Impairment		2,000
RARE Infrastructure, Ltd [Member] | Fund management contracts [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Goodwill and Intangible Asset Impairment		32,000
RARE Infrastructure, Ltd [Member]
Subsequent Event [Line Items]
Assets Under Management				$ 6,800,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			(9,701)
RARE Infrastructure, Ltd [Member] | Change in Input Assumptions [Member]
Subsequent Event [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			$ (10,000)
RARE Infrastructure, Ltd [Member] | Change in Input Assumptions [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		$ 11,500