Investments (Details 10) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 71.2	$ 75.7
30-59 days past due	33.1	85.0
60-89 days past due	8.5	13.0
90 days or more past due	27.1	50.9
Total past due	68.7	148.9
Current	11,324.9	10,680.4
Mortgage loans, Total amortized cost	11,393.6	10,829.3	10,971.6
Recorded investment 90 days or more past due and accruing	7.5	7.5
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	9,988.1	9,461.4	9,576.2
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	31.1	46.8
30-59 days past due		61.4
60-89 days past due		4.4
90 days or more past due	2.4	22.5
Total past due	2.4	88.3
Current	9,442.1	8,803.5
Mortgage loans, Total amortized cost	9,444.5	8,891.8
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	543.6	569.6
Mortgage loans, Total amortized cost	543.6	569.6
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,405.5	1,367.9	1,395.4
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	25.5	13.2
30-59 days past due	8.7	7.8
60-89 days past due	3.1	2.6
90 days or more past due	3.6	6.2
Total past due	15.4	16.6
Current	504.1	594.4
Mortgage loans, Total amortized cost	519.5	611.0
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	14.6	15.7
30-59 days past due	24.4	15.8
60-89 days past due	5.4	6.0
90 days or more past due	21.1	22.2
Total past due	50.9	44.0
Current	835.1	712.9
Mortgage loans, Total amortized cost	886.0	756.9
Recorded investment 90 days or more past due and accruing	$ 7.5	$ 7.5