Long-term Equity-based Compensation - Schedule of Outstanding Options (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Subject to Awards	2,265,711	2,543,673
Weighted- average Exercise Price Per Share ($)	$ 39.74	$ 41.37
Weighted- average Remaining Contractual Life (in Years)	3 years 9 months 18 days
Range of Exercise Prices $10.00 - $15.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 10
Range of Exercise Prices, Upper Range Limit	$ 15
Shares Subject to Awards	15,000
Weighted- average Exercise Price Per Share ($)	$ 13.55
Weighted- average Remaining Contractual Life (in Years)	2 years 3 months 2 days
Shares Subject to Awards	15,000
Weighted- average Exercise Price Per Share ($)	$ 13.55
Range of Exercise Prices $15.01 - $20.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 15.01
Range of Exercise Prices, Upper Range Limit	$ 20
Shares Subject to Awards	8,000
Weighted- average Exercise Price Per Share ($)	$ 16.48
Weighted- average Remaining Contractual Life (in Years)	4 years 4 months 5 days
Shares Subject to Awards	8,000
Weighted- average Exercise Price Per Share ($)	$ 16.48
Range of Exercise Prices $20.01 - $25.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 20.01
Range of Exercise Prices, Upper Range Limit	$ 25
Shares Subject to Awards	29,000
Weighted- average Exercise Price Per Share ($)	$ 23.36
Weighted- average Remaining Contractual Life (in Years)	3 years 10 months 8 days
Shares Subject to Awards	29,000
Weighted- average Exercise Price Per Share ($)	$ 23.36
Range of Exercise Prices $25.01 - $30.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 25.01
Range of Exercise Prices, Upper Range Limit	$ 30
Shares Subject to Awards	379,000
Weighted- average Exercise Price Per Share ($)	$ 28.84
Weighted- average Remaining Contractual Life (in Years)	6 years 2 months 2 days
Shares Subject to Awards	332,998
Weighted- average Exercise Price Per Share ($)	$ 28.74
Range of Exercise Prices $30.01 - $35.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 30.01
Range of Exercise Prices, Upper Range Limit	$ 35
Shares Subject to Awards	226,250
Weighted- average Exercise Price Per Share ($)	$ 33.16
Weighted- average Remaining Contractual Life (in Years)	8 years 1 month 14 days
Shares Subject to Awards	130,500
Weighted- average Exercise Price Per Share ($)	$ 32.94
Range of Exercise Prices $35.01 - $40.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 35.01
Range of Exercise Prices, Upper Range Limit	$ 40
Shares Subject to Awards	573,250
Weighted- average Exercise Price Per Share ($)	$ 36.91
Weighted- average Remaining Contractual Life (in Years)	5 years 10 months 10 days
Shares Subject to Awards	393,498
Weighted- average Exercise Price Per Share ($)	$ 37.11
Range of Exercise Prices $40.01 - $45.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 40.01
Range of Exercise Prices, Upper Range Limit	$ 45
Shares Subject to Awards	184,902
Weighted- average Exercise Price Per Share ($)	$ 43.10
Weighted- average Remaining Contractual Life (in Years)	0 years 1 month 2 days
Shares Subject to Awards	184,902
Weighted- average Exercise Price Per Share ($)	$ 43.10
Range of Exercise Prices $45.01 - $50.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 45.01
Range of Exercise Prices, Upper Range Limit	$ 50
Shares Subject to Awards	793,541
Weighted- average Exercise Price Per Share ($)	$ 48.59
Weighted- average Remaining Contractual Life (in Years)	1 year 1 month 23 days
Shares Subject to Awards	793,541
Weighted- average Exercise Price Per Share ($)	$ 48.59
Range of Exercise Prices $50.01 - $55.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 50.01
Range of Exercise Prices, Upper Range Limit	$ 55
Shares Subject to Awards	56,768
Weighted- average Exercise Price Per Share ($)	$ 51.16
Weighted- average Remaining Contractual Life (in Years)	0 years 1 month 5 days
Shares Subject to Awards	56,768
Weighted- average Exercise Price Per Share ($)	$ 51.16
Range of Exercise Prices $10.00 - $55.00
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Lower Range Limit	$ 10.00
Range of Exercise Prices, Upper Range Limit	$ 55.00
Shares Subject to Awards	2,265,711
Weighted- average Exercise Price Per Share ($)	$ 39.74
Weighted- average Remaining Contractual Life (in Years)	3 years 9 months 25 days
Shares Subject to Awards	1,944,207
Weighted- average Exercise Price Per Share ($)	$ 40.59

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

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range10Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range5Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range6Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range7Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range8Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis=kmpr_Range9Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: