Investments (Realized Gains Losses Available-For-Sale Securities) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	$ 2.4	$ 8.2	$ 5.7	$ 18.0
Gross Realized Gains	0.1	0.5	0.4	1.2
Gross Realized Losses	0.0	0.0	0.0	0.0
Seed Money [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	0.6	6.8	1.8	15.7
Gross Realized Gains	0.1	0.4	0.4	1.0
Gross Realized Losses	0.0	0.0	0.0	0.0
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	0.8	1.4	1.3	2.3
Gross Realized Gains	0.0	0.1	0.0	0.2
Gross Realized Losses	0.0	$ 0.0	0.0	$ 0.0
Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	1.0		2.6
Gross Realized Gains	0.0		0.0
Gross Realized Losses	$ 0.0		$ 0.0

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

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- Definition

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26853-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

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