Consolidated Investment Products (Condensed Consolidating Statement Of Income Line Items Reflecting Impact Of Consolidation Of Investment Products Into The Condensed Consolidated Statements Of Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Total operating revenues	$ 4,177.0	$ 4,092.2	$ 3,487.7
Total operating expenses	3,305.5	3,194.1	2,897.8
Operating income/(loss)	871.5	898.1	589.9
Equity in earnings of unconsolidated affiliates	29.7	30.5	40.2
Interest and dividend income	268.3	318.2	251.3
Other investment income/(losses)	(89.4)	(89.9)	129.6
Interest expense	(220.6)	(248.8)	(177.2)
Income before income taxes	859.5	908.1	833.8
Income Tax Expense (Benefit)	(272.2)	(286.1)	(197.0)
Net income	587.3	622.0	636.8
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	89.8	107.7	(171.1)
Net income attributable to common shareholders	677.1	729.7	465.7
CLOs - VIEs [Member]
Total operating revenues	0	0	0
Total operating expenses	48.2	46.7	41.4
Operating income/(loss)	(48.2)	(46.7)	(41.4)
Equity in earnings of unconsolidated affiliates	0	0	0
Interest and dividend income	260.7	307.2	246.0
Other investment income/(losses)	(112.2)	(235.1)	(3.8)
Interest expense	(182.8)	(195.3)	(123.7)
Income before income taxes	(82.5)	(169.9)	77.1
Income Tax Expense (Benefit)	0	0	0
Net income	(82.5)	(169.9)	77.1
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	82.2	169.9	(77.1)
Net income attributable to common shareholders	(0.3)	0	0
Other VIEs [Member]
Total operating revenues	0	0	0
Total operating expenses	0.9	1.0	1.6
Operating income/(loss)	(0.9)	(1.0)	(1.6)
Equity in earnings of unconsolidated affiliates	0	0	0
Interest and dividend income	0	0	0
Other investment income/(losses)	2.4	1.0	6.9
Interest expense	0	0	0
Income before income taxes	1.5	0	5.3
Income Tax Expense (Benefit)	0	0	0
Net income	1.5	0	5.3
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	(1.5)	0	(5.3)
Net income attributable to common shareholders	0	0	0
VOEs [Member]
Total operating revenues	0	0.1	0.3
Total operating expenses	23.4	12.6	12.3
Operating income/(loss)	(23.4)	(12.5)	(12.0)
Equity in earnings of unconsolidated affiliates	0	0	0
Interest and dividend income	0	0	0
Other investment income/(losses)	13.7	74.9	104.5
Interest expense	0	0	0
Income before income taxes	(9.7)	62.4	92.5
Income Tax Expense (Benefit)	0	0	0
Net income	(9.7)	62.4	92.5
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	9.1	(62.3)	(88.4)
Net income attributable to common shareholders	(0.6)	0.1	4.1
VIE Adjustments [Member]
Total operating revenues	(41.0)	(47.3)	(45.3)
Total operating expenses	(41.0)	(47.3)	(45.3)
Operating income/(loss)	0	0	0
Equity in earnings of unconsolidated affiliates	0.5	(0.2)	(0.6)
Interest and dividend income	(14.5)	(8.3)	(5.1)
Other investment income/(losses)	(10.3)	20.3	6.4
Interest expense	14.5	8.3	5.1
Income before income taxes	(9.8)	20.1	5.8
Income Tax Expense (Benefit)	0	0	0
Net income	(9.8)	20.1	5.8
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	0	0	(0.1)
Net income attributable to common shareholders	(9.8)	20.1	5.7
Consolidated Investment Products [Member]
Total operating revenues	(41.0)	(47.2)	(45.0)
Total operating expenses	31.5	13.0	10.0
Operating income/(loss)	(72.5)	(60.2)	(55.0)
Equity in earnings of unconsolidated affiliates	0.5	(0.2)	(0.6)
Interest and dividend income	246.2	298.9	240.9
Other investment income/(losses)	(106.4)	(138.9)	114.0
Interest expense	(168.3)	(187.0)	(118.6)
Income before income taxes	(100.5)	(87.4)	180.7
Income Tax Expense (Benefit)	0	0	0
Net income	(100.5)	(87.4)	180.7
(Gains)/losses attributable to noncontrolling interests in consolidated entities, net	89.8	107.6	(170.9)
Net income attributable to common shareholders	$ (10.7)	$ 20.2	$ 9.8