Consolidated Investment Entities (Fair Value Measurement) (Details) (USD $)	9 Months Ended	2 Months Ended	9 Months Ended	12 Months Ended					9 Months Ended				9 Months Ended			9 Months Ended
	Sep. 30, 2014	Jul. 31, 2014 LIBOR Line of Credit	Sep. 30, 2014 LIBOR Line of Credit	Dec. 31, 2013 EURIBOR Line of Credit	Sep. 30, 2014 VOEs Private Equity Funds	Dec. 31, 2013 VOEs Private Equity Funds	Sep. 30, 2014 VOEs Securities Sold under Agreements to Repurchase	Dec. 31, 2013 VOEs Securities Sold under Agreements to Repurchase	Sep. 30, 2014 VOEs EURIBOR Private Equity Funds	Sep. 30, 2014 VIEs Corporate Loans Senior Secured Corporate Loans	Dec. 31, 2013 VIEs Corporate Loans Senior Secured Corporate Loans	Sep. 30, 2014 VIEs Corporate Loans Senior Secured Corporate Loans LIBOR or Prime Maximum	Sep. 30, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans	May 28, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans	Dec. 31, 2013 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans	Sep. 30, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans LIBOR	Sep. 30, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans LIBOR Minimum	Sep. 30, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans LIBOR Maximum	Sep. 30, 2014 VIEs Collateralized Debt Obligations Senior Secured Floating Rate Leveraged Loans Prime	Sep. 30, 2014 Consolidated investment entities fund	Dec. 31, 2013 Consolidated investment entities fund
Variable Interest Entity [Line Items]
Consolidated funds																				35	35
Basis spread												9.50%
Unpaid principal exceeds fair value, amount										$ 39,700,000	$ 9,700,000		$ 203,500,000		$ 139,600,000
Default of Collateral Assets, Percentage										1.00%	1.00%
Debt Instrument, Description of Variable Rate Basis	LIBOR								EURIBOR							LIBOR			PRIME
Basis spread		1.40%	1.60%	2.20%													0.22%	7.00%
Weighted average maturity													9 years 1 month 6 days
Revolving lines of credit	9,977,900,000				550,000,000	400,000,000
Asset coverage, percentage					250.00%	350.00%
Outstanding borrowings	5,674,400,000				273,000,000	212,200,000	361,000,000	147,500,000						60,000,000
Transfers in to Level 3	$ 13,900,000