Fair Value Measurements (Changes in the Balances of Level 3 Financial Assets) (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
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 46.2	$ 15.2	$ 11.4	$ 5.5
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Total gains or losses for the period
Realized in net income	18.2	(7.8)	53.2	1.9
Unrealized in accumulated other comprehensive income	0	0	0	0
Purchases, issues, sales and settlements
Purchases/additions	0	0	0	0
Issues	0	0	0	0
Sales	0	0	(0.2)	0
Settlements	0	0	0	0
Closing balance	64.4	7.4	64.4	7.4
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Available-For-Sale Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	0	0.2	0.2	0.2
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Total gains or losses for the period
Realized in net income	0	0	0	0
Unrealized in accumulated other comprehensive income	0	0	0	0
Purchases, issues, sales and settlements
Purchases/additions	0	0	0	0
Issues	0	0	0	0
Sales	0	0	(0.2)	0
Settlements		0	0	0
Closing balance	0	0.2	0	0.2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Embedded Contractual Derivative Asset [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	10.8	15.0	11.2	5.3
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Total gains or losses for the period
Realized in net income	1.9	(7.8)	1.5	1.9
Unrealized in accumulated other comprehensive income	0	0	0	0
Purchases, issues, sales and settlements
Purchases/additions	0	0	0	0
Issues	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Closing balance	12.7	7.2	12.7	7.2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Other Noncurrent Asset [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	35.4		0
Transfers into Level 3	0		0
Transfers out of Level 3	0		0
Total gains or losses for the period
Realized in net income	16.3		51.7
Unrealized in accumulated other comprehensive income	0		0
Purchases, issues, sales and settlements
Purchases/additions	0		0
Issues	0		0
Sales	0		0
Settlements	0		0
Closing balance	51.7		51.7
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0		$ 0