Information About Segments of Business (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Consolidated Revenues [Abstract]
Consolidated revenues		$ 1,496.0	$ 1,545.7	$ 4,351.7	$ 4,285.9
Net premiums earned		1,238.6	1,259.4	3,582.1	3,520.7
Title, escrow and other fees		126.7	112.7	342.9	319.4
Total premiums and fees		1,365.4	1,372.1	3,925.1	3,840.1
Consolidated net realized investment gains (losses)		7.2	41.4	58.1	77.0
Total operating revenues		1,488.7	1,504.2	4,293.6	4,208.9
Consolidated Income (Loss) Before Taxes (Credits) [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		164.0	184.7	495.2	490.3
Consolidated net realized investment gains (losses)		7.2	41.4	58.1	77.0
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)		53.1	58.8	160.2	158.8
Income tax expense (credits) on consolidated net realized investment gains (losses)		2.5	14.5	20.3	26.9
Total Company Segments [Member]
Consolidated Revenues [Abstract]
Consolidated revenues		1,480.5	1,493.6	4,270.9	4,181.7
Consolidated Income (Loss) Before Taxes (Credits) [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest		152.8	139.5	428.2	405.4
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)		49.9	44.5	139.2	132.7
General Insurance Group [Member]
Consolidated Revenues [Abstract]
Net premiums earned		732.0	744.5	2,192.8	2,157.2
Net investment income and other income		104.5	110.9	314.2	311.3
Income (loss) before income taxes (credits) and realized investment gains or losses	[1]	75.9	97.0	243.1	264.1
Total operating revenues		836.5	855.4	2,507.1	2,468.5
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)		22.7	29.8	74.0	83.5
Interest charges on intercompany financing arrangements		13.2	10.5	38.6	31.0
Title Insurance Group [Member]
Consolidated Revenues [Abstract]
Net premiums earned		461.6	454.0	1,244.2	1,178.4
Title, escrow and other fees		126.7	112.7	342.9	319.4
Total premiums and fees		588.4	566.7	1,587.2	1,497.8
Net investment income and other income		9.2	9.1	28.0	25.9
Income (loss) before income taxes (credits) and realized investment gains or losses	[1]	58.5	55.0	124.5	118.7
Total operating revenues		597.7	575.9	1,615.2	1,523.7
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)		20.8	19.2	44.2	41.5
Interest charges on intercompany financing arrangements		2.1	2.0	6.3	6.1
RFIG Run-off Business [Member]
Segment Reporting Information
Deferred Payment Obligation						$ 657.0
Consolidated Revenues [Abstract]
Net premiums earned		40.4	55.8	131.0	170.3
Net investment income and other income		5.7	6.4	17.5	19.0
Income (loss) before income taxes (credits) and realized investment gains or losses		18.4	(12.5)	60.4	22.4
Total operating revenues		46.2	62.2	148.5	189.4
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)		6.3	(4.5)	20.9	7.6
Other sources - net [Member]
Consolidated Revenues [Abstract]
Consolidated revenues	[2]	32.1	31.1	89.2	89.1
Consolidated Income (Loss) Before Taxes (Credits) [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	[2]	3.9	3.7	8.8	7.9
Consolidated Income Tax Expense (Credits) [Abstract]
Income tax expense (credits)	[2]	0.5	(0.2)	0.6	(0.8)
Consolidation elimination adjustments [Member]
Consolidated Revenues [Abstract]
Consolidated revenues		$ (23.9)	$ (20.6)	$ (66.5)	$ (61.9)

[1] Income before taxes (credits) is reported net of interest charges on intercompany financing arrangements with Old Republic's holding company parent for the following segments: General - $13.2 and $38.6 compared to $10.5 and $31.0 for the quarter and nine months ended September 30, 2016 and 2015, respectively, and Title - $2.1 and $6.3 compared to $2.0 and $6.1 for the quarter and nine months ended September 30, 2016 and 2015, respectively.

[2] Represents amounts for Old Republic's holding company parent, minor corporate services subsidiaries, and a small life and accident insurance operation.