Investments (Details 10) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 39.8	$ 61.2
30-59 days past due	34.4	36.8
60-89 days past due	7.6	8.4
90 days or more past due	27.4	36.8
Total past due	69.4	82.0
Current	11,475.5	11,521.4
Mortgage loans, Total amortized cost	11,544.9	11,603.4	11,667.4
Recorded investment 90 days or more past due and accruing	6.9	7.3
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	10,299.0	10,327.7	10,286.5
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	13.2	33.2
30-59 days past due	0.5
90 days or more past due	8.3	16.7
Total past due	8.8	16.7
Current	9,879.0	9,864.4
Mortgage loans, Total amortized cost	9,887.8	9,881.1
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	411.2	446.6
Mortgage loans, Total amortized cost	411.2	446.6
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,245.9	1,275.7	1,380.9
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	16.1	16.6
30-59 days past due	4.9	4.4
60-89 days past due	1.2	1.0
90 days or more past due	2.9	3.0
Total past due	9.0	8.4
Current	368.1	386.5
Mortgage loans, Total amortized cost	377.1	394.9
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	10.5	11.4
30-59 days past due	29.0	32.4
60-89 days past due	6.4	7.4
90 days or more past due	16.2	17.1
Total past due	51.6	56.9
Current	817.2	823.9
Mortgage loans, Total amortized cost	868.8	880.8
Recorded investment 90 days or more past due and accruing	$ 6.9	$ 7.3