Investments (Details 10) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 35.6	$ 61.2
30-59 days past due	26.3	36.8
60-89 days past due	7.2	8.4
90 days or more past due	18.0	36.8
Total past due	51.5	82.0
Current	11,751.4	11,521.4
Mortgage loans, Total amortized cost	11,802.9	11,603.4	11,956.0
Recorded investment 90 days or more past due and accruing	5.8	7.3
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	10,596.8	10,327.7	10,658.3
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	10.7	33.2
90 days or more past due	0.9	16.7
Total past due	0.9	16.7
Current	10,219.8	9,864.4
Mortgage loans, Total amortized cost	10,220.7	9,881.1
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	376.1	446.6
Mortgage loans, Total amortized cost	376.1	446.6
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,206.1	1,275.7	1,297.7
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	15.1	16.6
30-59 days past due	2.5	4.4
60-89 days past due	2.4	1.0
90 days or more past due	2.2	3.0
Total past due	7.1	8.4
Current	315.3	386.5
Mortgage loans, Total amortized cost	322.4	394.9
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	9.8	11.4
30-59 days past due	23.8	32.4
60-89 days past due	4.8	7.4
90 days or more past due	14.9	17.1
Total past due	43.5	56.9
Current	840.2	823.9
Mortgage loans, Total amortized cost	883.7	880.8
Recorded investment 90 days or more past due and accruing	$ 5.8	$ 7.3