Income Taxes - Schedule of Liabilities for Income Tax (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Accrued Income Taxes, Current	$ 7.8us-gaap_AccruedIncomeTaxesCurrent	$ 1.5us-gaap_AccruedIncomeTaxesCurrent
Deferred Income Tax Liabilities	21.5us-gaap_DeferredIncomeTaxLiabilities	0us-gaap_DeferredIncomeTaxLiabilities
Unrecognized Tax Benefits	7.2us-gaap_UnrecognizedTaxBenefits	6.8us-gaap_UnrecognizedTaxBenefits	6.4us-gaap_UnrecognizedTaxBenefits	6.2us-gaap_UnrecognizedTaxBenefits
Liabilities for Income Taxes	$ 36.5kmpr_LiabilitiesForIncomeTaxes	$ 8.3kmpr_LiabilitiesForIncomeTaxes

Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all currently due domestic and foreign income tax obligations.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.20)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Article 9

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph b(1)

-Article 7

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