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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 10.9	$ 16.2	$ 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	(0.1)	(1.0)	(0.4)	9.7
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	10.8	15.2	10.8	15.2
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	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
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	0	0	0	0
Embedded Contractual Derivative Asset [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	10.9	16.0	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	(0.1)	(1.0)	(0.4)	9.7
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	10.8	15.0	10.8	15.0
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	$ 0	$ 0	$ 0	$ 0