Investments (Details 12) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Commercial mortgage loans
Impaired mortgage loans
Recorded investment in impaired mortgage loans	$ 10.7		$ 10.7		$ 25.9
Unpaid principal balance of impaired mortgage loans	12.0		12.0		37.1
Related allowance for impaired mortgage loans	3.1		3.1		2.4
Average investment in impaired mortgage loans	8.0	34.8	18.3	33.7
Interest income recognized on impaired mortgage loans	0.1	0.2	0.3	0.4
Brick and mortar
Impaired mortgage loans
Recorded investment in impaired mortgage loans with no related allowance	0.9		0.9		21.5
Recorded investment in impaired mortgage loans with related allowance	9.8		9.8		4.4
Unpaid principal balance of impaired mortgage loans with no related allowance	2.2		2.2		32.7
Unpaid principal balance of impaired mortgage loans with related allowance	9.8		9.8		4.4
Related allowance for impaired mortgage loans	3.1		3.1		2.4
Average investment in impaired mortgage loans with no related allowance	0.9	6.4	11.2	16.2
Average investment in impaired mortgage loans with related allowance	7.1	28.4	7.1	17.5
Interest income recognized on impaired mortgage loans with no related allowance		0.1	0.1	0.2
Interest income recognized on impaired mortgage loans with related allowance	0.1	0.1	0.2	0.2
Residential mortgage loans
Impaired mortgage loans
Recorded investment in impaired mortgage loans	29.6		29.6		33.0
Unpaid principal balance of impaired mortgage loans	31.1		31.1		32.1
Related allowance for impaired mortgage loans	9.4		9.4		10.2
Average investment in impaired mortgage loans	30.1	35.7	31.4	37.2
Interest income recognized on impaired mortgage loans	0.2	0.4	0.6	0.9
Home equity
Impaired mortgage loans
Recorded investment in impaired mortgage loans with related allowance	17.6		17.6		19.5
Unpaid principal balance of impaired mortgage loans with related allowance	19.2		19.2		19.7
Related allowance for impaired mortgage loans	8.5		8.5		9.2
Average investment in impaired mortgage loans with related allowance	18.0	20.2	18.6	20.3
Interest income recognized on impaired mortgage loans with related allowance	0.2	0.4	0.5	0.8
First liens
Impaired mortgage loans
Recorded investment in impaired mortgage loans with no related allowance	4.0		4.0		4.6
Recorded investment in impaired mortgage loans with related allowance	8.0		8.0		8.9
Unpaid principal balance of impaired mortgage loans with no related allowance	4.0		4.0		4.6
Unpaid principal balance of impaired mortgage loans with related allowance	7.9		7.9		7.8
Related allowance for impaired mortgage loans	0.9		0.9		1.0
Average investment in impaired mortgage loans with no related allowance	4.1	6.2	4.3	7.9
Average investment in impaired mortgage loans with related allowance	8.0	9.3	8.5	9.0
Interest income recognized on impaired mortgage loans with related allowance			$ 0.1	$ 0.1