Investments (Details 10) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	$ 31.2	$ 33.4
30-59 days past due	20.0	26.5
60-89 days past due	7.2	12.7
90 days or more past due	18.4	16.2
Total past due	45.6	55.4
Current	11,910.8	11,812.7
Mortgage loans, Total amortized cost	11,956.4us-gaap_NotesReceivableGross	11,868.1us-gaap_NotesReceivableGross	11,544.9us-gaap_NotesReceivableGross
Recorded investment 90 days or more past due and accruing	4.4	4.5
Commercial mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	10,820.8	10,723.8	10,299.0
Brick and mortar
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	8.9	9.6
60-89 days past due		4.5
90 days or more past due	4.5	0.7
Total past due	4.5	5.2
Current	10,481.8	10,369.7
Mortgage loans, Total amortized cost	10,486.3	10,374.9
Credit tenant loans
Mortgage loan non-accrual and aging disclosures
Current	334.5	348.9
Mortgage loans, Total amortized cost	334.5	348.9
Residential mortgage loans
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Total amortized cost	1,135.6	1,144.3	1,245.9
Home equity
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	13.2	15.0
30-59 days past due	1.7	2.3
60-89 days past due	1.0	1.2
90 days or more past due	1.6	3.4
Total past due	4.3	6.9
Current	263.8	276.5
Mortgage loans, Total amortized cost	268.1	283.4
First liens
Mortgage loan non-accrual and aging disclosures
Mortgage loans, Non-accrual status	9.1	8.8
30-59 days past due	18.3	24.2
60-89 days past due	6.2	7.0
90 days or more past due	12.3	12.1
Total past due	36.8	43.3
Current	830.7	817.6
Mortgage loans, Total amortized cost	867.5	860.9
Recorded investment 90 days or more past due and accruing	$ 4.4	$ 4.5

Financing receivables that are less than 30 days past due.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524

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Financing receivables that are less than 60 days past due but more than 29 days past due.

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Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524

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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10(3))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Subparagraph 3

-Article 9

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