Business Segments - Segment Information (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	$ 8.4	$ 44.3	$ 28.8	$ 158.2
Operating Income Loss, Net Of Taxes	9.8	30.6	31.1	112.2
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	(0.8)	46.9	49.9	160.1
Earned Premiums	543.0	568.2	1,637.1	1,727.8
Net Investment Income	58.6	79.4	222.7	241.0
Other Income	0.4	0.4	0.8	1.0
Net Realized Gains on Sales of Investments	(4.2)	7.2	27.8	14.6
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net	(5.0)	(4.6)	(6.7)	(12.7)
Revenues	592.8	650.6	1,881.7	1,971.7
Equity in Net Income (Loss) of Investee	0	(0.3)	0	(0.1)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	3.8	32.3	44.8	113.4
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	21.6	50.5	60.6	176.2
Operating Income Loss, Net Of Taxes	18.1	32.4	50.6	120.7
Revenues	600.9	645.2	1,854.6	1,960.3
Kemper [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	(15.7)	17.1	(55.7)	54.0
Operating Income Loss, Net Of Taxes	(8.0)	13.5	(29.7)	41.6
Earned Premiums	216.5	221.8	642.8	667.1
Net Investment Income	8.4	12.3	38.1	38.6
Other Income	0.1	0.1	0.2	0.3
Revenues	225.0	234.2	681.1	706.0
Unitrin Specialty [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	6.7	8.0	17.8	23.0
Operating Income Loss, Net Of Taxes	5.3	6.2	14.4	18.0
Earned Premiums	111.0	117.0	336.7	359.9
Net Investment Income	3.3	5.7	16.4	18.5
Other Income	0.2	0.2	0.4	0.5
Revenues	114.5	122.9	353.5	378.9
Unitrin Direct [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	(3.7)	(1.5)	(19.3)	(1.7)
Operating Income Loss, Net Of Taxes	(1.6)	0.3	(10.1)	0.8
Earned Premiums	54.4	68.6	171.8	217.6
Net Investment Income	2.9	4.8	13.9	16.0
Other Income	0.1	0	0.1	0.1
Revenues	57.4	73.4	185.8	233.7
Life and Health [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	34.3	26.9	117.8	100.9
Operating Income Loss, Net Of Taxes	22.4	12.4	76.0	60.3
Earned Premiums	161.1	160.8	485.8	483.2
Net Investment Income	42.9	53.8	148.3	158.4
Other Income	0	0.1	0.1	0.1
Revenues	204.0	214.7	634.2	641.7
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	(13.2)	(6.2)	(31.8)	(18.0)
Operating Income Loss, Net Of Taxes	(8.3)	(1.8)	(19.5)	(8.5)
Net Investment Income	1.1	2.8	6.0	9.5
Net Realized Gains on Sales of Investments	(2.7)	4.7	18.0	9.5
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net	$ (3.3)	$ (3.0)	$ (4.3)	$ (8.3)