Catastrophe Reinsurance (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Reinsurance Disclosures [Abstract]
Catastrophic Events Classification	$ 25.0

Loss Threshold For Catastrophic Events Classification by ISO

No definition available.

Name:	kmpr_LossThresholdForCatastrophicEventsClassification
Namespace Prefix:	kmpr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration