Business Segments - Segment Information (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	$ (1.5)	$ 39.6	$ 54.3	$ 86.6
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	(8.8)	56.4	70.5	122.6
Earned Premiums	548.1	578.1	1,094.1	1,159.6
Net Investment Income	83.0	81.8	164.6	162.6
Other Income	0.2	0.3	0.4	0.6
Net Realized Gains on Sales of Investments	17.9	2.9	32.4	7.4
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net	(1.3)	(4.9)	(1.7)	(8.1)
Other Cost and Expense, Operating	(9.3)	(5.7)	(18.5)	(11.8)
Revenues	660.7	684.9	1,318.1	1,379.4
Automobile Finance Revenues	12.8	26.7	28.3	57.3
Equity in Net Income (Loss) of Investee	0	(0.5)	0	0.2
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	(1.5)	39.1	54.3	86.8
Operating Segments [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	(6.9)	44.1	45.5	94.0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	(16.1)	64.1	58.3	135.1
Revenues	641.6	683.4	1,282.5	1,373.4
Kemper [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	(33.0)	13.5	(21.7)	28.1
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	(54.2)	17.6	(40.0)	36.9
Earned Premiums	214.4	222.9	426.3	445.3
Net Investment Income	15.6	13.9	29.7	26.3
Other Income	0	0.1	0.1	0.2
Revenues	230.0	236.9	456.1	471.8
Unitrin Specialty [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	4.9	6.0	9.1	11.8
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	6.0	7.5	11.1	15.0
Earned Premiums	113.3	120.5	225.7	242.9
Net Investment Income	6.8	6.7	13.1	12.8
Other Income	0.1	0.1	0.2	0.3
Revenues	120.2	127.3	239.0	256.0
Unitrin Direct [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	(4.7)	0.4	(8.5)	0.5
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	(8.2)	0.9	(15.6)	(0.2)
Earned Premiums	57.5	73.0	117.4	149.0
Net Investment Income	5.6	5.9	11.0	11.2
Other Income	0	0.1	0	0.1
Revenues	63.1	79.0	128.4	160.3
Life and Health [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	20.9	21.5	53.6	47.9
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	32.7	33.5	83.5	74.0
Earned Premiums	162.9	161.7	324.7	322.4
Net Investment Income	52.4	51.3	105.4	104.6
Other Income	0.1	0	0.1	0
Revenues	215.4	213.0	430.2	427.0
Fireside Bank [Member]
Segment Reporting Information [Line Items]
Income (Loss) from Continuing Operations before Equity in Net Income (Loss) of Investee	5.0	2.7	13.0	5.7
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest	7.6	4.6	19.3	9.4
Net Investment Income	0.1	0.5	0.5	1.0
Revenues	12.9	27.2	28.8	58.3
Automobile Finance Revenues	12.8	26.7	28.3	57.3
Unallocated Amount to Segment [Member]
Segment Reporting Information [Line Items]
Net Investment Income	2.5	3.5	4.9	6.7
Net Realized Gains on Sales of Investments	11.6	1.9	21.0	4.8
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net	(0.7)	(3.2)	(1.0)	(5.3)
Other Expense Net	$ (5.5)	$ (3.2)	$ (11.2)	$ (6.9)