Investments (Credit Quality Indicators For Commercial Mortgage Loans) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Gross commercial mortgage loans	$ 1,276,015	$ 1,291,514
% of Gross Mortgage Loans	100.00%	100.00%
Debt-Service Coverage Ratio	1.94	1.89
Less valuation allowance	(3,399)	(4,482)
Net commercial mortgage loans	1,272,616	1,287,032
70% and less
Financing Receivable, Recorded Investment [Line Items]
Gross commercial mortgage loans	1,168,454	1,143,200
% of Gross Mortgage Loans	91.60%	88.50%
Debt-Service Coverage Ratio	2.01	1.97
71 – 80%
Financing Receivable, Recorded Investment [Line Items]
Gross commercial mortgage loans	73,762	73,603
% of Gross Mortgage Loans	5.80%	5.70%
Debt-Service Coverage Ratio	1.26	1.44
81 – 95%
Financing Receivable, Recorded Investment [Line Items]
Gross commercial mortgage loans	27,268	58,752
% of Gross Mortgage Loans	2.10%	4.60%
Debt-Service Coverage Ratio	1.04	1.19
Greater than 95%
Financing Receivable, Recorded Investment [Line Items]
Gross commercial mortgage loans	$ 6,531	$ 15,959
% of Gross Mortgage Loans	0.50%	1.20%
Debt-Service Coverage Ratio	0.43	0.87

Credit Quality Percentage for Gross Commercial Mortgage Loans

No definition available.

Name:	aiz_CreditQualityPercentageForGrossCommercialMortgageLoans
Namespace Prefix:	aiz_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt-Service Coverage Ratios for Commercial Mortgage Loans

+ References

No definition available.

+ Details

Name:	aiz_DebtServiceCoverageRatiosForCommercialMortgageLoans
Namespace Prefix:	aiz_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The allowance for commercial loan and lease losses represents the reserve to cover probable credit losses related to specifically identified commercial loans and leases, as well as probable credit losses inherent in the remainder of the commercial loan portfolio as of the balance sheet date. For banks, include currently required allocated transfer risk reserves. Include carryover of or adjustments to the allowance for commercial loan losses in connection with business combinations determined to be appropriate.

+ 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 210.9-03.7(d))

-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 7

-Subparagraph d

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18832-111554

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section S99

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18805-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableCommercialAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5066-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a)(3))

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

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9

+ Details

Name:	us-gaap_LoansReceivableCommercialMortgage
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(c))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph c

-Article 7

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateCommercialAndConsumerNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=aiz_LoanToValueEightyOneToNinetyFivePercentageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=aiz_LoanToValueGreaterThanNinetyFivePercentageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=aiz_LoanToValueSeventyOneToEightyPercentageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=aiz_LoanToValueSeventyPercentageAndLessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: