Consolidated Investment Products (VIE Balance Sheets Consolidated In Period) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	$ 535.7	$ 742.2
Accounts receivable and other assets of CIP	137.6	106.2
Investments of CIP	4,890.5	5,116.1
Total assets	26,598.9	25,734.3
Debt of CIP	4,272.9	4,403.1
Other liabilities of CIP	490.9	673.4
Total liabilities	18,558.0	17,838.8
Total equity	7,833.2	7,611.8	$ 7,962.5	$ 8,695.7
Total liabilities and equity	26,598.9	$ 25,734.3
CLOs - VIEs [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	8.2		14.4
Accounts receivable and other assets of CIP	1.3		0.0
Investments of CIP	45.8		10.9
Total assets	55.3		25.3
Debt of CIP	15.1		0.0
Other liabilities of CIP	13.7		0.7
Total liabilities	28.8		0.7
Total equity	26.5		24.6
Total liabilities and equity	55.3		25.3
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member] | CLOs - VIEs [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	10.9		17.7
Accounts receivable and other assets of CIP	3.2		1.1
Investments of CIP	139.9		77.4
Total assets	154.0		96.2
Other liabilities of CIP	1.9		2.3
Total liabilities	1.9		2.3
Total equity	152.1		93.9
Total liabilities and equity	154.0		$ 96.2
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member] | VOEs [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents of CIP	0.0
Accounts receivable and other assets of CIP	0.2
Investments of CIP	49.8
Total assets	50.0
Other liabilities of CIP	0.0
Total liabilities	0.0
Total equity	50.0
Total liabilities and equity	$ 50.0