Postretirement Benefits Other Than Pensions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014 employees	Dec. 31, 2013
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of retired employees covered	500
Number of active employees covered	300
Effect of one percentage point increase on accumulated postretirement benefit obligation	$ 1.7	$ 2.1
Effect of one percentage point increase on service and interest cost components	0.1	0.1
Amounts that will be amortized from AOCI in next Fiscal Year	(1.5)
Estimated future employer contributions in next fiscal year	$ 3.2
Medical Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next fiscal year	8.00%	8.50%
Health care cost trend rate assumed for future years	5.00%	5.00%
Prescription Drug Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next fiscal year	7.50%	8.00%
Health care cost trend rate assumed for future years	5.00%	5.00%

Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Future Years

No definition available.

Name:	kmpr_DefinedBenefitPlanHealthCareCostTrendRateAssumedForFutureYears
Namespace Prefix:	kmpr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Other Postretirement Benefit Plan, Number of Active Employees Covered

+ References

No definition available.

+ Details

Name:	kmpr_OtherPostretirementBenefitPlanNumberOfActiveEmployeesCovered
Namespace Prefix:	kmpr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Other Postretirement Benefit Plan, Number of Retired Employees Covered

+ References

No definition available.

+ Details

Name:	kmpr_OtherPostretirementBenefitPlanNumberOfRetiredEmployeesCovered
Namespace Prefix:	kmpr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanAmountToBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (l)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Health Care Cost Trend Rate

-URI http://asc.fasb.org/extlink&oid=6514820

+ Details

Name:	us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=kmpr_MedicalBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=kmpr_PrescriptionDrugBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: