Investments (Details 11) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 75.7	$ 97.1
30-59 days past due	85.0	28.4
60-89 days past due	13.0	35.5
90 days or more past due	50.9	41.3
Total past due	148.9	105.2
Current	10,680.4	11,141.0
Mortgage loans, Total amortized cost	10,829.3	11,246.2
Recorded investment 90 days or more past due and accruing	7.5	10.0
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	9,461.4	9,689.6
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	46.8	67.1
30-59 days past due	61.4
60-89 days past due	4.4	22.5
90 days or more past due	22.5	9.1
Total past due	88.3	31.6
Current	8,803.5	9,041.4
Mortgage loans, Total amortized cost	8,891.8	9,073.0
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	569.6	616.6
Mortgage loans, Total amortized cost	569.6	616.6
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,367.9	1,556.6
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	13.2	14.3
30-59 days past due	7.8	9.3
60-89 days past due	2.6	4.5
90 days or more past due	6.2	9.2
Total past due	16.6	23.0
Current	594.4	696.3
Mortgage loans, Total amortized cost	611.0	719.3
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	15.7	15.7
30-59 days past due	15.8	19.1
60-89 days past due	6.0	8.5
90 days or more past due	22.2	23.0
Total past due	44.0	50.6
Current	712.9	786.7
Mortgage loans, Total amortized cost	756.9	837.3
Recorded investment 90 days or more past due and accruing	$ 7.5	$ 10.0