Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income (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
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized Investment Gains (Losses)	$ 10.7	$ (14.0)	$ (6.7)	$ (16.5)
Income tax expense (benefit)	(16.9)	0.5	(18.8)	19.3
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	0		2.7
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized Investment Gains (Losses)	0.3		0.5
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	0.3		0.5
Income tax expense (benefit)	0.1		0.2
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	0.2		0.3
Accumulated Other-than-Temporary Impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized Investment Gains (Losses)	(0.3)		3.7
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	(0.3)		3.7
Income tax expense (benefit)	(0.1)		1.3
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (0.2)		$ 2.4