Condensed Consolidated Statements Of Changes In Equity (USD $) In Millions, unless otherwise specified	Total	Common Shares [Member]	Additional Paid-In-Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Retained Earnings Appropriated For Investors In Consolidated Investment Products [Member]	Accumulated Other Comprehensive Income [Member]	Total Equity Attributable To Common Shareholders [Member]	Noncontrolling Interests In Consolidated Entities [Member]
Beginning balance, value at Dec. 31, 2010	$ 9,360.9	$ 98.1	$ 6,262.6	$ (991.5)	$ 1,904.4	$ 495.5	$ 495.5	$ 8,264.6	$ 1,096.3
Net income	228.7				360.5			360.5	(131.8)
Other comprehensive income	155.6	0	0	0	0	0	149.0	149.0	6.6
Total comprehensive income	384.3							509.5	(125.2)
Other comprehensive income:
Net income (loss) reclassified to appropriated retained earnings	0					(170.2)		(170.2)	170.2
Currency translation differences on investments in overseas subsidiaries reclassified to appropriated retained earnings	0					14.9		14.9	(14.9)
Change in noncontrolling interests in consolidated entities, net	(116.9)							0	(116.9)
Dividends	(108.5)				(108.5)			(108.5)
Employee share plans:
Share-based compensation	56.8		56.8					56.8
Vested shares	0		(175.6)	175.6				0
Exercise of options	9.9		(6.3)	16.2				9.9
Tax impact of share-based payment	15.1		15.1					15.1
Purchase of shares	(403.8)			(403.8)				(403.8)
Ending Balance, value at Jun. 30, 2011	9,197.8	98.1	6,152.6	(1,203.5)	2,156.4	340.2	644.5	8,188.3	1,009.5
Beginning balance, value at Dec. 31, 2011	9,137.6	98.1	6,180.6	(1,280.4)	2,413.2	334.3	373.3	8,119.1	1,018.5
Net income	302.4	0	0	0	347.8	0	0	347.8	(45.4)
Other comprehensive income	(8.0)	0	0	0	0	0	16.6	16.6	(24.6)
Total comprehensive income	294.4							364.4	(70.0)
Other comprehensive income:
Net income (loss) reclassified to appropriated retained earnings	0	0	0	0	0	(26.4)	0	(26.4)	26.4
Currency translation differences on investments in overseas subsidiaries reclassified to appropriated retained earnings	0	0	0	0	0	(8.5)	0	(8.5)	8.5
Deconsolidation of consolidated investment products	(47.6)	0	0	0	0	(47.6)	0	(47.6)	0
Change in noncontrolling interests in consolidated entities, net	(30.4)	0	0	0	0	0	0	0	(30.4)
Dividends	(133.7)	0	0	0	(133.7)	0	0	(133.7)	0
Employee share plans:
Share-based compensation	67.0	0	67.0	0	0	0	0	67.0	0
Vested shares	0	0	(147.7)	147.7	0	0	0	0	0
Exercise of options	12.1	0	(11.7)	23.8	0	0	0	12.1	0
Tax impact of share-based payment	12.0	0	12.0		0	0	0	12.0	0
Purchase of shares	(192.6)	0	0	(192.6)	0	0	0	(192.6)	0
Ending Balance, value at Jun. 30, 2012	$ 9,118.8	$ 98.1	$ 6,100.2	$ (1,301.5)	$ 2,627.3	$ 251.8	$ 389.9	$ 8,165.8	$ 953.0