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Amount of the excess of amortized cost basis over fair value of securities that have been in a loss position for less than twelve months for securities categorized neither as held-to-maturity nor trading securities.

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

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The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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Investments (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	Dec. 31, 2012
Investments
Carrying Value	$ 912.2		$ 912.2		$ 922.1
Available-for-sale securities
Book cost basis	179.4		179.4		200.9
Gross unrealized gains	477.2		477.2		412.5
Gross unrealized losses	(0.7)		(0.7)		(1.9)
Market value	655.9		655.9		611.5
Proceeds from sale of investments			235.9	257.7
Gross realized gains	50.5	59.1	136.0	83.9
Gross realized losses	0.5	0.8	1.6	2.9
Unrealized losses related to other than temporary investment impairments	0.4	0.4	0.9	2.3
Other than Temporary impairment
Lower of cost or market valuation adjustments on cost method investments	0.1	0.2	0.4	0.9
Common Stock
Fair value of investments by the length of time that the securities have been in a continuous loss position
Less than 12 months	19.7		19.7		25.7
Total	19.7		19.7		25.7
Unrealized losses of investments by the length of time that the securities have in a continuous loss position
Less than 12 months	0.7		0.7		1.9
Total	0.7		0.7		1.9
Private Equity Funds
Investments
Carrying Value	198.4		198.4		231.4
Future capital commitments
Future capital commitments related to private equity fund investments	7.0		7.0
Available-for-sale securities
Investments
Carrying Value	655.9		655.9		611.5
Available-for-sale securities \| State Street Corporation
Investments
Carrying Value	518.2		518.2		436.3
Available-for-sale securities \| Other available-for-sale securities
Investments
Carrying Value	137.7		137.7		175.2
Other investments
Investments
Carrying Value	256.3		256.3		310.6
Other investments \| Trading securities
Investments
Carrying Value	41.8		41.8		46.8
Other investments \| Held-to-maturity
Investments
Carrying Value	0		0		14.9
Other investments \| Cost method, private equity and other investments
Investments
Carrying Value	$ 214.5		$ 214.5		$ 248.9