Condensed Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating activities:
Net income	$ 302.4	$ 228.7
Adjustments to reconcile net income to net cash used in operating activities:
Amortization and depreciation	50.9	60.0
Share-based compensation expense	67.0	56.8
Gains on disposal of property, equipment, and software, net	(0.5)	0
Purchase of trading investments	(5,210.0)	(5,556.8)
Proceeds from sale of trading investments	5,200.8	5,516.5
Other gains and losses, net	(10.9)	(13.9)
(Gains)/losses of consolidated investment products, net	44.7	150.2
Tax benefit from share-based compensation	42.3	72.2
Excess tax benefits from share-based compensation	(12.0)	(15.1)
Equity in earnings of unconsolidated affiliates	(16.6)	(17.5)
Dividends from unconsolidated affiliates	13.1	3.0
Changes in operating assets and liabilities:
(Increase)/decrease in cash held by consolidated investment products	(45.9)	31.5
(Increase)/decrease in receivables	263.1	(260.4)
Increase/(decrease) in payables	(441.2)	(109.2)
Net cash (used in)/provided by operating activities	247.2	146.0
Investing activities:
Purchase of property and equipment	(37.2)	(40.7)
Disposal of property and equipment	0.6	0
Purchase of available-for-sale investments	(67.5)	(28.0)
Proceeds from sale of available-for-sale investments	23.8	36.6
Purchase of investments by consolidated investment products	(1,584.6)	(2,075.3)
Proceeds from sale of investments by consolidated investment products	1,537.0	2,300.9
Returns of capital in investments of consolidated investment products	(44.9)	75.5
Purchase of other investments	(63.4)	(61.4)
Proceeds from sale of other investments	46.2	23.7
Returns of capital and distributions from unconsolidated partnership investments	8.7	18.9
Acquisition of businesses	0	(14.9)
Acquisition earn-out payments	(5.6)	(5.4)
Net cash (used in)/provided by investing activities	(186.9)	229.9
Financing activities:
Proceeds from exercises of share options	12.1	9.9
Purchases of treasury shares	(150.0)	(333.0)
Dividends paid	(133.7)	(108.5)
Excess tax benefits from share-based compensation	12.0	15.1
Capital invested into consolidated investment products	19.4	32.5
Capital distributed by consolidated investment products	(35.5)	(134.9)
Net borrowings/(repayments) of debt of consolidated investment products	145.7	(246.3)
Net borrowings/(repayments) under credit facility	272.0	268.0
Repayments of senior notes	(215.1)
Payments to Acquire Interest in Subsidiaries and Affiliates	0	(12.3)
Net cash provided by/(used in) financing activities	(73.1)	(509.5)
(Decrease)/increase in cash and cash equivalents	(12.8)	(133.6)
Foreign exchange movement on cash and cash equivalents	3.8	14.6
Cash and cash equivalents, beginning of period	727.4	740.5
Cash and cash equivalents, end of period	718.4	621.5
Supplemental Cash Flow Information:
Interest paid	(26.4)	(27.2)
Interest received	2.5	4.5
Taxes paid	$ (96.2)	$ (109.9)