Fair Value Of Assets And Liabilities (Reconciliation Of Balance, Fair Value Measurement, Level 3) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Significant Unobservable Inputs [Member] | EURIBOR [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Probability of Default	1.00%				1.00%
Spread over variable rate	21.50%				21.50%
Significant Unobservable Inputs [Member] | EURIBOR [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Probability of Default	5.00%				5.00%
Spread over variable rate	28.50%				28.50%
Significant Unobservable Inputs [Member] | LIBOR [Member] | Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Probability of Default	1.00%				1.00%
Spread over variable rate	13.50%				13.50%
Significant Unobservable Inputs [Member] | LIBOR [Member] | Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Probability of Default	4.00%				4.00%
Spread over variable rate	18.00%				18.00%
Cost Valuation [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Other Debt Securities Excluded	$ 6.3				$ 6.3
Underlying Consolidated Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes Payable Excluded	12.6				12.6
CLO Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Beginning balance (Asset)	2.8		0.7		0		0.5
Deconsolidation of consolidated investment products	0				2.5
Change in unrealized gains and losses related to assets still held at end of period	0.1		0.1		0.1		0.1
Net unrealized gains and losses included in accumulated other comprehensive income/(loss) (Asset)	(0.2)	[1]	(0.2)	[1]	0.1	[1]	0	[1]
Gains and losses included in the Condensed Consolidated Statements of Income, Liabilities	0	[1]			0	[1]
reclassification	0				0
Gains and losses included in the Condensed Consolidated Statements of Income, Assets	0		0		0		0
Ending balance (Asset)	2.5	[2]	0.4		2.5	[2]	0.4
Other Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Beginning balance (Asset)	6.3				0
Deconsolidation of consolidated investment products	0				0
Change in unrealized gains and losses related to assets still held at end of period	0				(1.7)
Net unrealized gains and losses included in accumulated other comprehensive income/(loss) (Asset)	0	[1]			0	[1]
Gains and losses included in the Condensed Consolidated Statements of Income, Liabilities	0	[1]			0	[1]
reclassification	0				4.6
Gains and losses included in the Condensed Consolidated Statements of Income, Assets	0				0
Ending balance (Asset)	6.3				6.3
Note Payable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Beginning Balance (Liability)	(12.3)		18.5		(16.8)		18.9
Deconsolidation of consolidated investment products	0				0
Change in unrealized gains and losses related to assets still held at end of period	0		(2.9)		0		(2.9)
Net unrealized gains and losses included in accumulated other comprehensive income/(loss) (Asset)	0	[1]	0	[1]	0	[1]	0	[1]
Gains and losses included in the Condensed Consolidated Statements of Income, Liabilities	0	[1]			3.5	[1]
reclassification	0				0
Gains and losses included in the Condensed Consolidated Statements of Income, Assets	(0.3)		(0.5)		0.7		(0.1)
Ending Balance (Liability)	$ (12.6)		$ 16.1		$ (12.6)		$ 16.1

[1] Of these net unrealized gains and losses included in accumulated other comprehensive income/(loss), $0.2 million loss and $0.1 million gain for the three and six months ended June 30, 2012 is attributed to the change in unrealized gains and losses related to assets still held at June 30, 2012 (three and six months ended June 30, 2011: $0.2 million and none unrealized gains and losses related to assets still held at June 30, 2011). Of these net unrealized gains and losses included in earnings, none and $3.5 million for the three and six months ended June 30, 2012 is attributed to the change in unrealized gains and losses related to the note payable still held at June 30, 2012 (three and six months ended June 30, 2011: none and none).

[2] Other debt securities of $6.3 million are not included in the table above as they are valued using a cost valuation technique. The note payable of $12.6 million is also not included in the table above as its value is linked to the underlying value of consolidated funds. Both items are more fully discussed in the "Available-for-sale investments" and "Note payable" disclosures above.