Other Comprehensive Income/(Loss) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Foreign currency translation adjustments	$ (48.8)	[1]	$ 77.3	[1]	$ 488.3	[1]
Currency Translation Differences On Investments In Overseas Subsidiaries Reclassified To Appropriated Retained Earnings
Retained Earnings [Member]
Cumulative effect of initial adoption of FASB statement No.167			5.2
Currency Translation Differences On Investments In Overseas Subsidiaries Reclassified To Appropriated Retained Earnings
Noncontrolling Interests in Consolidated Entities [Member]
Foreign currency translation adjustments	23.1		(5.3)
Currency Translation Differences On Investments In Overseas Subsidiaries Reclassified To Appropriated Retained Earnings	(8.7)		5.3
Retained Earnings Appropriated For Investors In Consolidated Investment Products [Member]
Currency Translation Differences On Investments In Overseas Subsidiaries Reclassified To Appropriated Retained Earnings	$ 8.7		$ (5.3)

[1] Included in this amount are net gains of $23.1 million for the year ended December 31, 2011 related to foreign currency translation adjustments attributable to consolidated investment products (year ended December 31, 2010: net losses of $5.3 million). Of this amount, $8.7 million is reclassified from accumulated other comprehensive income into retained earnings appropriated for investors in consolidated investment products (year ended December 31, 2010: $5.3 million).