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	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Total operating revenues	$ 1,171.8	$ 1,013.9	$ 3,419.5	$ 3,003.7
Total operating expenses	885.8	803.0	2,592.6	2,366.6
Operating income	286.0	210.9	826.9	637.1
Equity in earnings of unconsolidated affiliates	10.3	5.2	25.3	21.8
Income tax provision	(92.9)	(72.3)	(262.7)	(205.8)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	250.1	153.7	653.9	452.0
Income/(loss) from discontinued operations, net of taxes	(1.4)	3.2	(1.9)	7.3
Net income	248.7	156.9	652.0	459.3
Net (income)/loss attributable to noncontrolling interests in consolidated entities	(20.6)	13.7	0.9	59.1
Net income attributable to common shareholders	228.1	170.6	652.9	518.4
Consolidated Investment Products [Member]
Total operating revenues	(12.0)	(11.5)	(29.8)	(32.4)
Total operating expenses	13.0	2.3	24.8	23.1
Operating income	(25.0)	(13.8)	(54.6)	(55.5)
Equity in earnings of unconsolidated affiliates	(2.2)	(0.5)	(3.4)	0.1
Interest and dividend income	45.5	65.3	142.8	196.1
Other investment income/(losses)	26.4	(33.9)	3.7	(78.5)
Interest expense	(33.5)	(41.9)	(96.8)	(134.4)
Income from continuing operations before income taxes	11.2	(24.8)	(8.3)	(72.2)
Income tax provision	0	0	0	0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	11.2	(24.8)	(8.3)	(72.2)
Income/(loss) from discontinued operations, net of taxes	0	0	0	0
Net income	11.2	(24.8)	(8.3)	(72.2)
Net (income)/loss attributable to noncontrolling interests in consolidated entities	(20.6)	13.7	(1.5)	59.1
Net income attributable to common shareholders	(9.4)	(11.1)	(9.8)	(13.1)
CLOs - VIEs [Member]
Total operating revenues	0	0	0	0
Total operating expenses	23.4	9.9	48.9	34.0
Operating income	(23.4)	(9.9)	(48.9)	(34.0)
Equity in earnings of unconsolidated affiliates	0	0	0	0
Interest and dividend income	48.8	68.7	155.5	206.4
Other investment income/(losses)	23.4	(38.5)	(15.8)	(79.1)
Interest expense	(36.8)	(45.3)	(109.5)	(144.7)
Income from continuing operations before income taxes	12.0	(25.0)	(18.7)	(51.4)
Income tax provision	0	0	0	0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	12.0	(25.0)	(18.7)	(51.4)
Income/(loss) from discontinued operations, net of taxes	0	0	0	0
Net income	12.0	(25.0)	(18.7)	(51.4)
Net (income)/loss attributable to noncontrolling interests in consolidated entities	(11.9)	25.0	18.9	51.4
Net income attributable to common shareholders	0.1	0	0.2	0
Other VIEs [Member]
Total operating revenues	0	0	0	0
Total operating expenses	0.3	0.2	0.8	0.7
Operating income	(0.3)	(0.2)	(0.8)	(0.7)
Equity in earnings of unconsolidated affiliates	0	0	0	0
Interest and dividend income	0	0	0	0
Other investment income/(losses)	1.1	1.6	1.3	2.5
Interest expense	0	0	0	0
Income from continuing operations before income taxes	0.8	1.4	0.5	1.8
Income tax provision	0	0	0	0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	0.8	1.4	0.5	1.8
Income/(loss) from discontinued operations, net of taxes	0	0	0	0
Net income	0.8	1.4	0.5	1.8
Net (income)/loss attributable to noncontrolling interests in consolidated entities	(0.8)	(1.4)	(0.5)	(1.8)
Net income attributable to common shareholders	0	0	0	0
VOEs [Member]
Total operating revenues	0	0	0.4	0
Total operating expenses	1.3	3.7	5.3	20.8
Operating income	(1.3)	(3.7)	(4.9)	(20.8)
Equity in earnings of unconsolidated affiliates	0	0	0	0
Interest and dividend income	0	0	0	0
Other investment income/(losses)	11.3	14.2	28.6	11.2
Interest expense	0	0	0	0
Income from continuing operations before income taxes	10.0	10.5	23.7	(9.6)
Income tax provision	0	0	0	0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	10.0	10.5	23.7	(9.6)
Income/(loss) from discontinued operations, net of taxes	0	0	0	0
Net income	10.0	10.5	23.7	(9.6)
Net (income)/loss attributable to noncontrolling interests in consolidated entities	(7.9)	(9.9)	(19.9)	9.5
Net income attributable to common shareholders	2.1	0.6	3.8	(0.1)
VIE Adjustments [Member]
Total operating revenues	(12.0)	(11.5)	(30.2)	(32.4)
Total operating expenses	(12.0)	(11.5)	(30.2)	(32.4)
Operating income	0	0	0	0
Equity in earnings of unconsolidated affiliates	(2.2)	(0.5)	(3.4)	0.1
Interest and dividend income	(3.3)	(3.4)	(12.7)	(10.3)
Other investment income/(losses)	(9.4)	(11.2)	(10.4)	(13.1)
Interest expense	3.3	3.4	12.7	10.3
Income from continuing operations before income taxes	(11.6)	(11.7)	(13.8)	(13.0)
Income tax provision	0	0	0	0
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	(11.6)	(11.7)	(13.8)	(13.0)
Income/(loss) from discontinued operations, net of taxes	0	0	0	0
Net income	(11.6)	(11.7)	(13.8)	(13.0)
Net (income)/loss attributable to noncontrolling interests in consolidated entities	0	0	0	0
Net income attributable to common shareholders	$ (11.6)	$ (11.7)	$ (13.8)	$ (13.0)