Investments (Details 10) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 66.4	$ 80.8
30-59 days past due	35.4	60.8
60-89 days past due	9.8	21.6
90 days or more past due	41.7	23.7
Total past due	86.9	106.1
Current	12,129.7	11,511.0
Mortgage loans, Total amortized cost	12,216.6	11,617.1	11,244.8
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	10,918.7	10,235.1	9,874.0
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	32.3	44.5
30-59 days past due		32.8
60-89 days past due		13.7
90 days or more past due	19.7
Total past due	19.7	46.5
Current	10,416.9	9,658.5
Mortgage loans, Total amortized cost	10,436.6	9,705.0
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	482.1	530.1
Mortgage loans, Total amortized cost	482.1	530.1
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,297.9	1,382.0	1,370.8
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	20.8	23.1
30-59 days past due	4.1	5.7
60-89 days past due	1.5	2.8
90 days or more past due	2.8	3.9
Total past due	8.4	12.4
Current	433.5	483.3
Mortgage loans, Total amortized cost	441.9	495.7
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	13.3	13.2
30-59 days past due	31.3	22.3
60-89 days past due	8.3	5.1
90 days or more past due	19.2	19.8
Total past due	58.8	47.2
Current	797.2	839.1
Mortgage loans, Total amortized cost	856.0	886.3
Recorded investment 90 days or more past due and accruing	$ 8.2	$ 8.1