Investments (Details 10) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 137.4	$ 80.8
30-59 days past due	34.8	60.8
60-89 days past due	18.0	21.6
90 days or more past due	56.4	23.7
Total past due	109.2	106.1
Current	11,846.8	11,511.0
Mortgage loans, Total amortized cost	11,956.0	11,617.1	11,393.6
Recorded investment 90 days or more past due and accruing	8.2	8.1
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	10,658.3	10,235.1	9,988.1
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	110.7	44.5
30-59 days past due		32.8
60-89 days past due	10.2	13.7
90 days or more past due	36.2
Total past due	46.4	46.5
Current	10,148.0	9,658.5
Mortgage loans, Total amortized cost	10,194.4	9,705.0
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	463.9	530.1
Mortgage loans, Total amortized cost	463.9	530.1
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,297.7	1,382.0	1,405.5
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	14.3	23.1
30-59 days past due	5.1	5.7
60-89 days past due	1.4	2.8
90 days or more past due	1.6	3.9
Total past due	8.1	12.4
Current	408.7	483.3
Mortgage loans, Total amortized cost	416.8	495.7
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	12.4	13.2
30-59 days past due	29.7	22.3
60-89 days past due	6.4	5.1
90 days or more past due	18.6	19.8
Total past due	54.7	47.2
Current	826.2	839.1
Mortgage loans, Total amortized cost	880.9	886.3
Recorded investment 90 days or more past due and accruing	$ 8.2	$ 8.1