v2.4.0.6

Investments - Additional Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Investment Derivative	Sep. 30, 2011	Sep. 30, 2012 Investment Derivative	Sep. 30, 2011	Dec. 31, 2011
Investment [Line Items]
Proceeds from the sale of investments in available-for-sale securities			$ 761,757	$ 1,827,485
Number of securities account for gross unrealized loss	96		96
Number of interest rate swaps	2		2
Interest rate swaps liability	4,973		4,973
Fair value of securities sold but not yet purchased	57,198		57,198		55,942
Securities sold under agreements to repurchase, principal amount	226,098		226,098		191,718
Securities sold under agreements to repurchase, interest expense	341	361	676	836
Collateral pledged in support of the repurchase agreements	244,064		244,064
Reverse repurchase agreement	57,000		57,000
Securities received as collateral	57,000		57,000
Minimum
Investment [Line Items]
Securities sold under agreements to repurchase, interest rates			0.40%
Maximum
Investment [Line Items]
Securities sold under agreements to repurchase, interest rates			0.45%
Securities sold under agreements to repurchase, at contract value
Investment [Line Items]
Securities sold under agreements to repurchase, accrued interest	0		0
Corporate Bonds
Investment [Line Items]
Fair value of securities sold but not yet purchased	57,155		57,155
Equity securities
Investment [Line Items]
Fair value of securities sold but not yet purchased	$ 43		$ 43

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Investments in Reverse Repurchase Agreements

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Fair value of obligations incurred from short sales.

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Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

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