Acquisitions EnTrustPermal Restructuring (Details) - EnTrustPermal [Member] - USD ($) $ in Thousands		3 Months Ended	12 Months Ended		15 Months Ended
		Mar. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring		$ (24,035)		$ (41,619)
Restructuring and Related Cost, Cost Incurred to Date				85,081	$ 85,081
Restructuring and Related Cost, Incurred Cost				41,785
Restructuring Reserve		17,527		9,874	9,874	$ 0
Restructuring Reserve, Settled without Cash	[1]	1,734		7,819	9,553
Restructuring Reserve, Accrual Adjustment		41,562		33,966
Minimum [Member] | Scenario, Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 5,000
Maximum [Member] | Scenario, Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 6,000
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring		(21,938)		(29,211)
Restructuring and Related Cost, Cost Incurred to Date				59,486	59,486
Restructuring Reserve		9,643		3,323	3,323	0
Restructuring Reserve, Settled without Cash	[1]	591		4,423	5,014
Restructuring Reserve, Accrual Adjustment		31,581		22,891
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring		(2,097)		(12,408)
Restructuring and Related Cost, Cost Incurred to Date				25,595	25,595
Restructuring Reserve		7,884		6,551	6,551	$ 0
Restructuring Reserve, Settled without Cash	[1]	1,143		3,396	4,539
Restructuring Reserve, Accrual Adjustment	[2]	9,981		11,075
Commitments Related to Vacated Space that Remains Vacant [Member]
Restructuring Cost and Reserve [Line Items]
Valuation Allowances and Reserves, Balance		$ 7,212		$ 9,069	$ 9,069

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

[2] Includes lease loss reserve for space permanently abandoned of $9,069 for the year ended March 31, 2017, and $7,212 for the year ended March 31, 2016.