Fair Value Measurements (Changes in Level 3 Financial Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 10.0	$ 70.1
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	(2.3)	(60.1)
Unrealized in accumulated other comprehensive income	0.0	0.0
Purchases, issues, sales and settlements:
Purchases	0.0	0.0
Issuances	0.0	0.0
Sales	0.0	0.0
Settlements	(2.0)	0.0
Ending balance	5.7	10.0
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 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	10.0	7.2
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	(2.3)	2.8
Unrealized in accumulated other comprehensive income	0.0	0.0
Purchases, issues, sales and settlements:
Purchases	0.0	0.0
Issuances	0.0	0.0
Sales	0.0	0.0
Settlements	(2.0)	0.0
Ending balance	5.7	10.0
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	0.0	0.0
State-Sponsored Health Plans Settlement Account Deficit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	0.0	62.9
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	(62.9)
Unrealized in accumulated other comprehensive income	0.0	0.0
Purchases, issues, sales and settlements:
Purchases	0.0	0.0
Issuances	0.0	0.0
Sales	0.0	0.0
Settlements	0.0	0.0
Ending balance	0.0	0.0
Change in unrealized gains (losses) included in net income for assets held at the end of the reporting period	$ 0.0	$ 0.0