Shareholders' Equity - Narrative (Details) - USD ($)			12 Months Ended
	Jun. 07, 2019	Jul. 02, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2019
Schedule of Capitalization, Equity [Line Items]
Preferred stock, shares authorized (in shares)			20,000,000
Preferred stock, par value (in dollars per share)			$ 0.10
Common stock, shares authorized (in shares)			100,000,000	100,000,000
Common stock, par value (in dollars per share)			$ 0.10	$ 0.1
Preferred stock, shares issued (in shares)			0	0
Preferred stock, shares outstanding (in shares)			0	0
Common stock, shares outstanding (in shares)			66,665,888	64,756,833
Share-based compensation expense			$ 25,300,000	$ 18,600,000	$ 9,400,000
Stock repurchased and retired during period (in shares)			0	0	0
Percentage of authorized control Level RBC			200.00%
Dividends paid			$ 67,800,000	$ 56,400,000	$ 49,500,000
Amount available for dividend payment			1,300,000,000
Kemper's Insurance Subsidiaries
Schedule of Capitalization, Equity [Line Items]
Cash dividends paid by Kemper's Insurance Subsidiaries to Kemper			239,000,000.0
Amount available for dividend payments			435,400,000
Amount of restricted net assets for consolidated and unconsolidated subsidiaries			3,900,000,000
Life & Health Insurance | Kemper's Insurance Subsidiaries
Schedule of Capitalization, Equity [Line Items]
Statutory capital and surplus			408,000,000.0	454,700,000
Statutory net income			90,400,000	143,900,000	84,100,000
Statutory capital and surplus required			122,000,000.0
Property & Casualty Insurance Subsidiaries | Kemper's Insurance Subsidiaries
Schedule of Capitalization, Equity [Line Items]
Statutory capital and surplus			1,600,000,000	1,400,000,000
Statutory net income			347,600,000	$ 236,400,000	$ 56,900,000
Statutory capital and surplus required			$ 641,900,000
Subordinated Debentures due 2054 (Fair Value: 2018 – $151.1) | Subordinated Debt
Schedule of Capitalization, Equity [Line Items]
Long-term debt, gross	$ 150,000,000.0
Stated interest rate, percentage	7.375%		7.375%
Employee Stock Purchase Plan | Stock Options
Schedule of Capitalization, Equity [Line Items]
Number of exercisable options						1,300,000
Minimum annual contributions per employee, percent			1.00%
Maximum annual contributions per employee, percent			10.00%
Maximum annual contributions per employee, amount			$ 25,000
Discount from market price			15.00%
Shares issued under employee stock purchase plan (in shares)			24,080
Price per share (in dollars per share)			$ 66.08
Share-based compensation expense			$ 300,000
Investment-grade
Schedule of Capitalization, Equity [Line Items]
Number of shares issued in transaction (in shares)	1,552,500
Sale of stock, price per share (in dollars per share)	$ 83.00
Gross proceeds from issuance of common stock	$ 128,900,000
Transaction costs	1,700,000
Net proceeds from issuance of common stock	127,200,000
Accrued Liabilities and Other Liabilities | Investment-grade
Schedule of Capitalization, Equity [Line Items]
Transaction costs	$ 100,000
Infinity Property and Casualty Corporation
Schedule of Capitalization, Equity [Line Items]
Business acquisition, interest issued (in shares)		13,184,107
Share price		$ 74.53