Discontinued Operations (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest, Loan Fees and Earned Discounts	$ 0	$ 12.6	$ 0	$ 28.0
Other Income	0	0.2	0	0.3
Net Gain on Sale of Loans in Inactive Portfolio	1.1	0	12.4	0
Net Investment Income	0	0.1	0	0.5
Net Realized Gains on Sales of Investments	0	0.1	0	0.4
Total Revenues Included in Discontinued Operations	1.1	13.0	12.4	29.2
Income (Loss) from Discontinued Operations before Income Taxes:
Net Gain on Sale of Loans in Inactive Portfolio	1.1	0	12.4	0
Income from Discontinued Operations before Income Taxes	1.0	9.3	13.3	18.7
Income Tax Expense	(0.3)	(3.2)	(5.3)	(6.1)
Income from Discontinued Operations	0.7	6.1	8.0	12.6
Income from Discontinued Operations Per Unrestricted Share:
Basic (in dollars per share)	$ 0.01	$ 0.10	$ 0.14	$ 0.21
Diluted (in dollars per share)	$ 0.01	$ 0.10	$ 0.14	$ 0.21
Discontinued Operations, Property and Casualty Insurance Reserves	1,010.2	1,101.2	1,010.2	1,101.2	1,029.1	1,118.7
Fireside [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net Gain on Sale of Loans in Inactive Portfolio	1.1	0	12.4	0
Income (Loss) from Discontinued Operations before Income Taxes:
Results of Operations / Change in Estimate of Retained Liabilities Arising from Discontinued Operations	0	7.8	(0.2)	19.8
Net Gain on Sale of Loans in Inactive Portfolio	1.1	0	12.4	0
Income from Discontinued Operations Per Unrestricted Share:
Notional Amount of Sales of Loans Held-for-sale			283
Disposal Group, Including Discontinued Operation, Transaction, Shutdown, and Other Costs			13.8
Disposal Group, Including Discontinued Operation, Accrued Transaction Costs	0.8		0.8
Unitrin Business Insurance [Member]
Income (Loss) from Discontinued Operations before Income Taxes:
Results of Operations / Change in Estimate of Retained Liabilities Arising from Discontinued Operations	(0.1)	1.5	1.1	(1.1)
Income from Discontinued Operations Per Unrestricted Share:
Discontinued Operations, Property and Casualty Insurance Reserves	$ 112.3		$ 112.3		$ 125.6