Investments Gain on Securities, Net of Investment Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
(Loss) Gain on Investments [Line Items]
Gain (loss) on securities, net	$ 2,254	[1]	$ (2,293)	[1]	$ 5,056	[1]	$ 515	[1]
Proceeds from redemptions of securities avaliable for sale	6,400		15,900		75,948		26,795
Consolidated Investment Companies [Member]
(Loss) Gain on Investments [Line Items]
Gain (loss) on securities, net	1,100		(2,300)		1,600		(1,700)
Available-for-sale Securities [Member]
(Loss) Gain on Investments [Line Items]
Realized gains	1,034	[2],[3]	223	[2],[3]	3,142	[2],[3]	2,310	[2],[3]
Trading Securities [Member]
(Loss) Gain on Investments [Line Items]
Unrealized gain on trading securities	738		(1,963)		1,432		(1,688)
Realized gains	278	[2]	92	[2]	829	[2]	704	[2]
Realized losses	(68)	[2]	(214)	[2]	(415)	[2]	(529)	[2]
Derivatives [Member]
(Loss) Gain on Investments [Line Items]
Unrealized gain on derivatives	(64)	[4]	(163)	[4]	123	[4]	(270)	[4]
Realized gains	410	[2],[4]	23	[2],[4]	636	[2],[4]	429	[2],[4]
Realized losses	$ (74)	[2],[4]	$ (291)	[2],[4]	$ (691)	[2],[4]	$ (441)	[2],[4]

[1] Amounts related to consolidated investment companies totaled $1.1 million and $1.6 million for the three and nine months ended September 30, 2012, respectively, and $(2.3) million and $(1.7) million for the three and nine months ended September 30, 2011, respectively.

[2] Realized gains and losses are computed on a specific-identification basis.

[3] Amounts related to sales of available-for-sale securities resulting in proceeds of $6.4 million and $75.9 million for the three and nine months ended September 30, 2012, respectively, and $15.9 million and $26.8 million for the three and nine months ended September 30, 2011, respectively.

[4] Amounts related to the settlement of economic derivatives held by certain consolidated sponsored products.