Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Gains and losses on trading securities	$ (18.2)	$ 3.3
Net realized gains/losses transferred from accumulated other comprehensive income	4.7	8.2	8.6
Charges to other comprehensive income from other-than-temporary impairment related to non-credit factors	0
Seed Money [Member]
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment charges on seed money investments	$ 0.8	$ 1.0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Percentage Ownership In Private Equity, Real Estate, and Other Entities	5.00%

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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+ Details

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period. Trading securities are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) and the change in net unrealized holding gain (loss) is included in earnings for the period.

+ References

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+ Details