Consolidated Investment Products (Condensed Consolidating Balance Sheet Line Items Reflecting Impact Of Consolidation Of Investment Products Into The Condensed Consolidated Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	$ 445.0	$ 287.8
Accounts receivable and other assets of CIP	62.2	84.1
Investments of CIP	4,514.6	4,550.6
Total assets	18,763.5	17,492.4
Debt of CIP	4,003.1	3,899.4
Other liabilities of CIP	251.0	104.3
Total liabilities	9,644.1	8,443.4
Equity	9,119.4	9,049.0	9,197.4	9,137.6
Retained earnings appropriated for investors in consolidated investment products	106.3	128.8
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	578.9	727.8
Total liabilities and equity	18,763.5	17,492.4
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	7.1
Accounts receivable and other assets of CIP	15.2
Investments of CIP	76.1
Total assets	98.4
Debt of CIP	25.0
Other liabilities of CIP	36.0
Total liabilities	61.0
Equity	37.4
Total liabilities and equity	98.4
Consolidated Investment Products [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	445.0	287.8
Accounts receivable and other assets of CIP	62.2	84.1
Investments of CIP	4,514.6	4,550.6
Adjustments (1)	(82.5)	(71.1)
Total assets	4,939.3	4,851.4
Debt of CIP	4,003.1	3,899.4
Other liabilities of CIP	251.1	104.3
Adjustments (1)		(8.9)
Total liabilities	4,254.2	3,994.8
Retained earnings appropriated for investors in consolidated investment products	106.3	128.8
Other equity attributable to common shareholders	(0.9)	0
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	579.7	727.8
Total liabilities and equity	4,939.3	4,851.4
CLOs - VIEs [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	393.6	211.8
Accounts receivable and other assets of CIP	59.9	54.6
Investments of CIP	4,017.1	3,948.0
Adjustments (1)	0	0
Total assets	4,470.6	4,214.4
Debt of CIP	4,111.8	3,980.7
Other liabilities of CIP	252.4	105.3
Adjustments (1)		0
Total liabilities	4,364.2	4,086.0
Retained earnings appropriated for investors in consolidated investment products	106.7	128.8
Other equity attributable to common shareholders	(0.3)	(0.4)
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	0	0
Total liabilities and equity	4,470.6	4,214.4
Other VIEs [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	1.7	0.2
Accounts receivable and other assets of CIP	0.3	0.2
Investments of CIP	39.8	35.9
Adjustments (1)	0	0
Total assets	41.8	36.3
Debt of CIP	0	0
Other liabilities of CIP	0.6	0.5
Adjustments (1)		0
Total liabilities	0.6	0.5
Retained earnings appropriated for investors in consolidated investment products	0	0
Other equity attributable to common shareholders	(0.2)	(0.1)
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	41.4	35.9
Total liabilities and equity	41.8	36.3
VOEs [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	49.7	75.8
Accounts receivable and other assets of CIP	2.0	29.3
Investments of CIP	511.3	607.9
Adjustments (1)	0	15.8
Total assets	563.0	728.8
Debt of CIP	0	0
Other liabilities of CIP	2.8	2.9
Adjustments (1)		0
Total liabilities	2.8	2.9
Retained earnings appropriated for investors in consolidated investment products	(0.4)	0
Other equity attributable to common shareholders	22.3	34.0
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	538.3	691.9
Total liabilities and equity	563.0	728.8
VIE Adjustments [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	0	0
Accounts receivable and other assets of CIP	0	0
Investments of CIP	(53.6)	(41.2)
Adjustments (1)	(82.5)	(86.9)
Total assets	(136.1)	(128.1)
Debt of CIP	(108.7)	(81.3)
Other liabilities of CIP	(4.7)	(4.4)
Adjustments (1)		(8.9)
Total liabilities	(113.4)	(94.6)
Retained earnings appropriated for investors in consolidated investment products	0	0
Other equity attributable to common shareholders	(22.7)	(33.5)
Equity attributable to nonredeemable noncontrolling interests in consolidated entities	0	0
Total liabilities and equity	(136.1)	(128.1)
New CLO [Member] | CLOs - VIEs [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Cash and cash equivalents of CIP	573.4
Accounts receivable and other assets of CIP	15.4
Investments of CIP	738.3
Total assets	1,327.1
Debt of CIP	856.5
Other liabilities of CIP	462.0
Total liabilities	1,318.5
Equity	8.6
Total liabilities and equity	$ 1,327.1