Fair Value Measurements (Changes in the Balances of Level 3 Financial Assets) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 61.4	$ 31.7	$ 70.1	$ 11.4
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	(38.5)	14.5	(47.2)	35.0
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	(0.2)
Settlements	0	0	0	0
Closing balance	22.9	46.2	22.9	46.2
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	0	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	(0.2)
Settlements	0	0	0	0
Closing balance	0	0	0	0
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	11.4	10.9	7.2	11.2
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	1.9	(0.1)	6.1	(0.4)
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	13.3	10.8	13.3	10.8
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Other Noncurrent Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	50.0	20.8	62.9	0
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	(40.4)	14.6	(53.3)	35.4
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	9.6	35.4	9.6	35.4
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0	$ 0	$ 0