Other Gains and Losses, Net (Schedule of other gains and losses, net) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
OTHER GAINS AND LOSSES, NET
Gain on sale of investments	$ 9.4		$ 9.9		$ 5.9
Unrealized gain on trading investments, net	0		14.2		0
Net foreign exchange gains	0		0		8.4
Settlement of litigation	45.0	[1]	0	[1]	0	[1]
Net gain generated upon debt tender offer	0		0		3.3
Total other gains	54.4		24.1		17.6
Other-than-temporary impairment of available-for-sale investments	(1.0)		(7.0)		(8.2)
Unrealized loss on trading investments, net	(2.6)		0		0
Net foreign exhange losses	(0.6)		(0.2)		0
Other realized losses	(1.2)		(1.3)		(1.6)
Total other losses	(5.4)		(8.5)		(9.8)
Other gains and losses, net	$ 49.0		$ 15.6		$ 7.8

[1] Included within other gains and losses in the year ended December 31, 2011 is a credit of $45.0 million related to the settlement of litigation arising from the 2007 departure of certain investment professionals to a competitor.