Acquisitions Martin Currie Acquisition (Details) £ in Thousands, $ in Thousands		3 Months Ended				9 Months Ended	12 Months Ended
		Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2014 GBP (£)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2016 USD ($)		Mar. 31, 2015 USD ($)	Oct. 01, 2014 USD ($)
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current									$ 2,494
Business Combination, Contingent Consideration, Liability							$ 84,585		35,484		$ 110,784
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	[1]								530,399
Martin Currie [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Liability, Current									0
Business Combination, Contingent Consideration, Liability							41,222		11,775		$ 70,114	$ 75,211
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability						$ (29,447)
Payments to Acquire Businesses, Gross				£ 125,000	$ 202,577
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High								£ 325,000	$ 400,413	[1]
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] | Martin Currie [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability		$ (7,000)	$ (18,000)			(25,000)	(28,361)
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] | Martin Currie [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability						$ (4,447)	$ (531)

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