Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance	$ 4.0	$ (12.7)
Change in component during the period before reclassifications	1.8	(0.5)
Amounts reclassified from AOCI	(3.1)	(0.9)
Accumulated Other Comprehensive Income (Loss), ending balance	2.7	(14.1)
Net Unrealized Investment Losses [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance	4.4	3.0
Change in component during the period before reclassifications	(2.2)	1.1
Amounts reclassified from AOCI	(0.1)	(0.6)
Accumulated Other Comprehensive Income (Loss), ending balance	2.1	3.5
Portion of OTTI Losses Recognized in OCI [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss), beginning balance	(0.4)	(15.7)
Change in component during the period before reclassifications	4.0	(1.6)
Amounts reclassified from AOCI	(3.0)	(0.3)
Accumulated Other Comprehensive Income (Loss), ending balance	$ 0.6	$ (17.6)