Acquisitions QS Investors - Restructuring (Details) - QS Investors [Domain] - USD ($) $ in Thousands		3 Months Ended	12 Months Ended					24 Months Ended
		Mar. 31, 2014	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015		Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment		$ 2,272			$ 32,617
Payments for Restructuring			$ (1,522)	$ (2,548)	(28,598)
Restructuring Reserve		2,272	2,221	3,743	6,291		$ 2,272	$ 6,291	$ 0
Restructuring Reserve, Settled without Cash	[1]				3,229		286	3,515
Restructuring and Related Cost, Cost Incurred to Date					38,404			38,404
Restructuring and Related Cost, Incurred Cost					35,846
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment		2,161			22,897
Payments for Restructuring			0	(400)	(24,658)
Restructuring Reserve		2,161	0	0	400		2,161	400	0
Restructuring Reserve, Settled without Cash	[1]				1,659		0	1,659
Restructuring and Related Cost, Cost Incurred to Date					26,717			26,717
Commitments Related to Vacated Space that Remains Vacant [Member]
Restructuring Cost and Reserve [Line Items]
Valuation Allowances and Reserves, Balance			6,760
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment		111			9,720	[2]
Payments for Restructuring			(1,522)	(2,148)	(3,940)
Restructuring Reserve		$ 111	$ 2,221	$ 3,743	5,891		111	5,891	$ 0
Restructuring Reserve, Settled without Cash	[1]				1,570		$ 286	1,856
Restructuring and Related Cost, Cost Incurred to Date					$ 11,687			$ 11,687

[1] Includes stock-based compensation expense and accelerated fixed asset depreciation.

[2] Includes lease loss reserve of $6,760 for space permanently abandoned.