Acquisitions EnTrustPermal Restructuring (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended	15 Months Ended
		Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2015
EnTrust Capital [Member]
Restructuring Cost and Reserve [Line Items]
Revenues		$ 26,540		$ 45,266
EnTrustPermal [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring			$ (24,035)	(22,098)
Restructuring and Related Cost, Cost Incurred to Date		79,959		79,959	$ 79,959
Restructuring and Related Cost, Incurred Cost		12,400		36,663
Restructuring Reserve		26,556	17,527	26,556	26,556			$ 0
Restructuring Reserve, Settled without Cash	[1]		1,734	5,536	7,270
Restructuring Reserve, Accrual Adjustment			41,562	31,127
EnTrustPermal [Member] | Minimum [Member] | Scenario, Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges						$ 12,000	$ 92,000
EnTrustPermal [Member] | Maximum [Member] | Scenario, Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges						$ 15,000	$ 95,000
EnTrustPermal [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring			(21,938)	(13,012)
Restructuring and Related Cost, Cost Incurred to Date		53,979		53,979	53,979
Restructuring Reserve		16,298	9,643	16,298	16,298			0
Restructuring Reserve, Settled without Cash	[1]		591	2,140	2,731
Restructuring Reserve, Accrual Adjustment			31,581	19,667
EnTrustPermal [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Payments for Restructuring			(2,097)	(9,086)
Restructuring and Related Cost, Cost Incurred to Date		25,980		25,980	25,980
Restructuring Reserve		10,258	7,884	10,258	10,258			$ 0
Restructuring Reserve, Settled without Cash	[1]		1,143	3,396	4,539
Restructuring Reserve, Accrual Adjustment	[2]		9,981	11,460
EnTrustPermal [Member] | Commitments Related to Vacated Space that Remains Vacant [Member]
Restructuring Cost and Reserve [Line Items]
Valuation Allowances and Reserves, Balance		9,069	$ 7,212	9,069	$ 9,069
EnTrust Capital [Member]
Restructuring Cost and Reserve [Line Items]
Business Combination, Acquisition Related Costs		$ 299		$ 7,031

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

[2] (1) Includes lease loss reserve for space permanently abandoned of $9,069 for the six months ended September 30, 2016, and $7,212 for the year ended March 31, 2016.