Acquisition of Business (Narrative) (Details)		12 Months Ended
	Jul. 02, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) agent
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	44,010
Infinity [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	13,184,107
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Fair Value of the Restricted Units Granted	$ 3,300,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	982,500,000
Business Combination, Consideration Transferred, Other	1,600,000
Contingent Consideration Classified as Equity, Fair Value Disclosure	1,700,000
Payments to Acquire Businesses, Gross	564,600,000.0
Business Combination, Consideration Transferred, Liabilities Incurred	110,000,000
Business Combination, Number of Agents | agent		10,600
Premiums Written, Net		$ 1,400,000,000
Kemper's 2-12-18 Closing Price per share [Member] | Infinity [Member]
Business Acquisition [Line Items]
Total Merger Value	$ 1,500,000,000
Share Price | $ / shares	$ 74.53
Secured Debt [Member] | Infinity [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Liabilities Incurred	$ 250,000,000