Fair Value Measurements (Changes in the Balances of Level 3 Financial Assets) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 70.1	$ 11.4
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses for the period
Realized in net income	(8.7)	20.5
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	(0.2)
Closing balance	61.4	31.7
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Available-For-Sale Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	0	0.2
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses for the period
Realized in net income	0	0
Unrealized in accumulated other comprehensive income	0	0
Purchases, issues, sales and settlements
Purchases/additions	0	0
Issues	0	0
Sales	0	0
Settlements		(0.2)
Closing balance	0	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Embedded Contractual Derivative Asset [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	7.2	11.2
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Total gains or losses for the period
Realized in net income	4.2	(0.3)
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	11.4	10.9
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Other Noncurrent Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	62.9	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	(12.9)	20.8
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	50.0	20.8
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0	$ 0