Investments (Details 12) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Commercial mortgage loans
Impaired mortgage loans
Recorded investment in impaired mortgage loans	$ 65.6		$ 65.6		$ 114.0
Unpaid principal balance of impaired mortgage loans	70.3		70.3		114.3
Related allowance for impaired mortgage loans	5.7		5.7		16.3
Average investment in impaired mortgage loans	100.7	70.6	89.8	64.7
Interest income recognized on impaired mortgage loans	0.9	0.6	2.0	1.1
Brick and mortar
Impaired mortgage loans
Recorded investment in impaired mortgage loans with no related allowance	43.4		43.4
Recorded investment in impaired mortgage loans with related allowance	22.2		22.2		114.0
Unpaid principal balance of impaired mortgage loans with no related allowance	46.1		46.1		0.3
Unpaid principal balance of impaired mortgage loans with related allowance	24.2		24.2		114.0
Related allowance for impaired mortgage loans	5.7		5.7		16.3
Average investment in impaired mortgage loans with no related allowance	69.4	36.6	21.7	35.8
Average investment in impaired mortgage loans with related allowance	31.3	34.0	68.1	28.9
Interest income recognized on impaired mortgage loans with no related allowance	0.8	0.2	1.9	0.5
Interest income recognized on impaired mortgage loans with related allowance	0.1	0.4	0.1	0.6
Residential mortgage loans
Impaired mortgage loans
Recorded investment in impaired mortgage loans	31.6		31.6		27.4
Unpaid principal balance of impaired mortgage loans	31.2		31.2		26.9
Related allowance for impaired mortgage loans	4.6		4.6		3.2
Average investment in impaired mortgage loans	31.4	27.3	29.5	27.3
Interest income recognized on impaired mortgage loans	0.3	0.2	0.6	0.4
Home equity
Impaired mortgage loans
Recorded investment in impaired mortgage loans with related allowance	17.6		17.6		14.5
Unpaid principal balance of impaired mortgage loans with related allowance	17.3		17.3		14.2
Related allowance for impaired mortgage loans	3.3		3.3		1.9
Average investment in impaired mortgage loans with related allowance	17.0	12.4	16.0	12.3
Interest income recognized on impaired mortgage loans with related allowance	0.2	0.2	0.5	0.3
First liens
Impaired mortgage loans
Recorded investment in impaired mortgage loans with no related allowance	5.6		5.6		4.4
Recorded investment in impaired mortgage loans with related allowance	8.4		8.4		8.5
Unpaid principal balance of impaired mortgage loans with no related allowance	5.5		5.5		4.2
Unpaid principal balance of impaired mortgage loans with related allowance	8.4		8.4		8.5
Related allowance for impaired mortgage loans	1.3		1.3		1.3
Average investment in impaired mortgage loans with no related allowance	5.9	4.0	5.0	4.7
Average investment in impaired mortgage loans with related allowance	8.5	10.9	8.5	10.3
Interest income recognized on impaired mortgage loans with related allowance	$ 0.1		$ 0.1	$ 0.1