Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 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]	Jun. 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					$ 23.5	$ 18.0	$ 20.3	$ 25.4	$ 22.1	$ 23.5
Unrealized gains included in earnings	6.1	3.1	6.7	3.5
Unrealized losses included in earnings	(0.6)	(0.2)	(2.0)	(2.0)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0.4	0	0.4
Settlements	0	0	(1.5)	0
Fair value, end of period					$ 23.5	$ 18.0	$ 20.3	$ 25.4	$ 22.1	$ 23.5