Discontinued Operations (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012 Fireside [Member]	Sep. 30, 2011 Fireside [Member]	Sep. 30, 2012 Fireside [Member]	Sep. 30, 2011 Fireside [Member]	Sep. 30, 2012 Unitrin Business Insurance [Member]	Sep. 30, 2011 Unitrin Business Insurance [Member]	Sep. 30, 2012 Unitrin Business Insurance [Member]	Sep. 30, 2011 Unitrin Business Insurance [Member]	Dec. 31, 2011 Unitrin Business Insurance [Member]	Dec. 31, 2011 Active Loan Portfolio [Member] Fireside [Member]	Sep. 30, 2012 Inactive Loan Portfolio [Member] Fireside [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest, Loan Fees and Earned Discounts	$ 0	$ 3.8	$ 0	$ 31.8
Other Income	0	1.1	0	1.4
Net Gain on Sale of Loan Portfolios	0.5	4.5	12.9	4.5			0.5	4.5	12.9	4.5						4.5	12.9
Net Investment Income	0	0	0	0.5
Net Realized Gains on Sales of Investments	0	0	0	0.4
Total Revenues Included in Discontinued Operations	0.5	9.4	12.9	38.6
Income (Loss) from Discontinued Operations before Income Taxes:
Results of Operations / Change in Estimate of Retained Liabilities Arising from Discontinued Operations							0	(2.0)	(0.2)	17.8	(0.6)	(1.9)	0.5	(3.0)
Net Gain on Sale of Loan Portfolios	0.5	4.5	12.9	4.5			0.5	4.5	12.9	4.5						4.5	12.9
Income (Loss) from Discontinued Operations before Income Taxes	(0.1)	0.6	13.2	19.3
Income Tax Benefit (Expense)	0.1	0.3	(5.2)	(5.8)
Income from Discontinued Operations	0	0.9	8.0	13.5
Income from Discontinued Operations Per Unrestricted Share:
Basic (in dollars per share)	$ 0.00	$ 0.02	$ 0.14	$ 0.22
Diluted (in dollars per share)	$ 0.00	$ 0.02	$ 0.14	$ 0.22
Notional Amount of Sales of Loans Held-for-sale																	283
Disposal Group, Including Discontinued Operation, Transaction, Shutdown, and Other Costs																	13.3
Disposal Group, Including Discontinued Operation, Accrued Transaction Costs																	4.7
Discontinued Operations, Property and Casualty Insurance Reserves	$ 981.8	$ 1,063.6	$ 981.8	$ 1,063.6	$ 1,029.1	$ 1,118.7					$ 110.0		$ 110.0		$ 125.6