Derivative Financial Instruments - Collateral and Credit Default Swaps (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Collateralized loan obligations notes, at fair value using the fair value option	$ 5,525,500,000		$ 5,161,600,000
Fair value of credit default swaps included in Derivatives assets	1,167,800,000		1,275,800,000
Fair value of credit default swaps included in Derivatives liabilities	4,078,700,000		4,076,400,000
Maturity period of derivative	5 years
Credit contracts | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Maximum potential future net exposure on sale of credit default swaps	1,700,000,000
Purchased protection on credit default swaps	500,000,000
Credit contracts | Not Designated as Hedging Instrument | Derivatives
Derivatives, Fair Value [Line Items]
Fair value of credit default swaps included in Derivatives assets	35,300,000	[1]	40,500,000	[1]
Fair value of credit default swaps included in Derivatives liabilities	12,400,000	[1]	14,500,000	[1]
Over the counter | Cash collateral, included in Payables
Derivatives, Fair Value [Line Items]
Collateralized loan obligations notes, at fair value using the fair value option	283,700,000		214,700,000
Cleared derivative contract | Cash collateral, included in Payables
Derivatives, Fair Value [Line Items]
Collateralized loan obligations notes, at fair value using the fair value option	$ 39,100,000		$ 18,800,000

[1] Open derivative contracts are reported as Derivatives assets or liabilities on the Condensed Consolidated Balance Sheets at fair value.