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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains (losses)	$ (2.1)	$ 10.7	$ (36.0)	$ (6.7)
Income tax expense (benefit)	5.9	(16.9)	4.0	(18.8)
Amounts Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	0.3	0	1.2	2.7
Net unrealized gains / (losses) on investments where credit-related OTTI was recognized:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains (losses)	0.2	0.3	1.2	0.5
Total before income taxes	0.2	0.3	1.2	0.5
Income tax expense (benefit)	0	0.1	0.4	0.2
Net income (loss)	0.2	0.2	0.8	0.3
Net unrealized investment gains / (losses) on all other investments:
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized capital gains (losses)	0.2	(0.3)	0.6	3.7
Total before income taxes	0.2	(0.3)	0.6	3.7
Income tax expense (benefit)	0.1	(0.1)	0.2	1.3
Net income (loss)	$ 0.1	$ (0.2)	$ 0.4	$ 2.4