Income Taxes - Schedule of Current and Deferred Income Tax Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current Income Tax Liabilities	$ 0us-gaap_AccruedIncomeTaxesCurrent	$ 7.8us-gaap_AccruedIncomeTaxesCurrent
Deferred Income Tax Liabilities	51.1us-gaap_DeferredIncomeTaxLiabilities	21.5us-gaap_DeferredIncomeTaxLiabilities
Unrecognized Tax Benefits	7.1us-gaap_UnrecognizedTaxBenefits	7.2us-gaap_UnrecognizedTaxBenefits
Liabilities for Income Taxes	$ 58.2kmpr_LiabilitiesForIncomeTaxes	$ 36.5kmpr_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