Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]	Dec. 31, 2012 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]	Sep. 30, 2012 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]	Mar. 31, 2012 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Venture Capital Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, beginning of period					$ 27.6	$ 23.5	$ 20.3	$ 25.2	$ 25.4	$ 23.5
Unrealized gains included in earnings	3.8	1.4	10.5	4.9
Unrealized losses included in earnings	0	(1.6)	(2.0)	(3.6)
Purchases	0.3	0	0.3	0.4
Settlements	0	0	(1.5)	0
Fair value, end of period					$ 27.6	$ 23.5	$ 20.3	$ 25.2	$ 25.4	$ 23.5