Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Common Stock	Dec. 31, 2013 Common Stock	Sep. 30, 2014 Cost method and other investments	Dec. 31, 2013 Cost method and other investments	Sep. 30, 2014 Private Equity Funds	Dec. 31, 2013 Private Equity Funds	Sep. 30, 2014 Available-for-sale securities	Dec. 31, 2013 Available-for-sale securities	Sep. 30, 2014 Available-for-sale securities State Street Corporation	Dec. 31, 2013 Available-for-sale securities State Street Corporation	Sep. 30, 2014 Available-for-sale securities Other available-for-sale securities	Dec. 31, 2013 Available-for-sale securities Other available-for-sale securities	Sep. 30, 2014 Other investments	Dec. 31, 2013 Other investments	Sep. 30, 2014 Other investments Trading securities	Dec. 31, 2013 Other investments Trading securities	Sep. 30, 2014 Other investments Cost method and other investments	Dec. 31, 2013 Other investments Cost method and other investments
Investments
Carrying Value	$ 733.0		$ 733.0		$ 881.3			$ 14.5	$ 15.7	$ 146.2	$ 167.3	$ 543.7	$ 654.0	$ 417.2	$ 515.5	$ 126.5	$ 138.5	$ 189.3	$ 227.3	$ 28.6	$ 44.3	$ 160.7	$ 183.0
Deferred Tax Liabilities, Other												169.5	201.1
Available-for-sale securities
Book cost basis	153.2		153.2		166.9
Available-for-sale Securities, Gross Unrealized Gain, Accumulated Investments	392.5		392.5		487.5
Available-for-sale Securities, Gross Unrealized Loss, Accumulated Investments	(2.0)		(2.0)		(0.4)
Market value	543.7		543.7		654.0
Proceeds from sale of investments			162.4	235.9
Gross realized gains	50.8	50.5	99.0	136.0
Gross realized losses	0.7	0.5	1.0	1.6
Unrealized losses related to other than temporary investment impairments	1.2	0.4	1.3	0.9
Fair value of investments by the length of time that the securities have been in a continuous loss position
Less than 12 months						25.3	5.9
Total						25.3	5.9
Unrealized losses of investments by the length of time that the securities have in a continuous loss position
Less than 12 months						2.0	0.4
Total						2.0	0.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value						0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Loss						0	0
Future capital commitments
Future capital commitments related to private equity fund investments										6.7
Investment Income, Dividend								33.2
Cost-method Investments, Realized Gain (Loss)			103.6
Other than Temporary impairment
Lower of cost or market valuation adjustments on cost method investments	$ 0.4	$ 0.1	$ 2.0	$ 0.4