Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 segment Units		Mar. 31, 2013		Dec. 31, 2013		Dec. 31, 2012
Segment Information
Number of Major Underwriting Units	2
Net written premiums	$ 311.1		$ 265.1
Earned premiums	276.5		286.5
Loss and loss adjustment expense	(149.4)		(148.9)
Policy acquisition expenses	(46.7)		(54.8)
Other underwriting expenses	(49.4)		(49.3)
Total underwriting income (loss)	31.0		33.5
Net investment income	10.0		9.4
Net realized and change in unrealized investment gains	18.9		28.4
Net other revenues	1.0		24.0
General and administrative expenses	(3.3)		(4.0)
Interest expense	(3.2)		(3.2)
Pre-tax income from continuing operations	54.4		88.1
Segment Information, Additional Disclosure
Total investment securities	2,415.7				2,364.9
Reinsurance recoverables	83.1	[1]			89.9
Deferred acquisition costs	105.9				103.7
Unpaid loss and loss adjustment expense reserves	1,069.8		1,010.3		1,054.3		1,000.0
Unearned premiums	582.2				544.9
Debt	274.7				274.7
Loss and LAE Ratio	54.00%	[2]	52.00%	[2]
Expense Ratio	34.80%	[2]	36.30%	[2]
Combined Ratio	88.80%	[2]	88.30%	[2]
Number of underwriting segments	14
Specialty Products
Segment Information
Net written premiums	160.8		123.9
Earned premiums	135.4		153.7
Loss and loss adjustment expense	(78.0)		(78.6)
Policy acquisition expenses	(21.4)		(30.4)
Other underwriting expenses	(22.2)		(24.3)
Total underwriting income (loss)	13.8		20.4
Net investment income	0		0
Net realized and change in unrealized investment gains	0		0
Net other revenues	0.1		0.3
General and administrative expenses	0.1		0
Interest expense	0		0
Pre-tax income from continuing operations	14.0		20.7
Segment Information, Additional Disclosure
Total investment securities	0				0
Reinsurance recoverables	56.2				60.2
Deferred acquisition costs	55.4				53.6
Unpaid loss and loss adjustment expense reserves	617.6				607.8
Unearned premiums	303.8				275.4
Debt	0				0
Loss and LAE Ratio	57.60%	[2]	51.20%	[2]
Expense Ratio	32.20%	[2]	35.50%	[2]
Combined Ratio	89.80%	[2]	86.70%	[2]
Number of underwriting segments	8
Specialty Industries
Segment Information
Net written premiums	150.3		141.2
Earned premiums	141.1		132.8
Loss and loss adjustment expense	(71.4)		(70.3)
Policy acquisition expenses	(25.3)		(24.4)
Other underwriting expenses	(27.2)		(25.0)
Total underwriting income (loss)	17.2		13.1
Net investment income	0		0
Net realized and change in unrealized investment gains	0		0
Net other revenues	0.1		0.2
General and administrative expenses	(0.5)		(0.6)
Interest expense	0		0
Pre-tax income from continuing operations	16.8		12.7
Segment Information, Additional Disclosure
Total investment securities	0				0
Reinsurance recoverables	26.9				29.7
Deferred acquisition costs	50.5				50.1
Unpaid loss and loss adjustment expense reserves	452.2				446.5
Unearned premiums	278.4				269.5
Debt	0				0
Loss and LAE Ratio	50.60%	[2]	52.90%	[2]
Expense Ratio	37.20%	[2]	37.20%	[2]
Combined Ratio	87.80%	[2]	90.10%	[2]
Number of underwriting segments	6
Investing, Financing and Corporate
Segment Information
Earned premiums	0		0
Loss and loss adjustment expense	0		0
Policy acquisition expenses	0		0
Other underwriting expenses	0		0
Total underwriting income (loss)	0		0
Net investment income	10.0		9.4
Net realized and change in unrealized investment gains	18.9		28.4
Net other revenues	0.8		23.5
General and administrative expenses	(2.9)		(3.4)
Interest expense	(3.2)		(3.2)
Pre-tax income from continuing operations	23.6		54.7
Segment Information, Additional Disclosure
Total investment securities	2,415.7	[3]			2,364.9	[3]
Reinsurance recoverables	0	[3]			0	[3]
Deferred acquisition costs	0	[3]			0	[3]
Unpaid loss and loss adjustment expense reserves	0	[3]			0	[3]
Unearned premiums	0	[3]			0	[3]
Debt	274.7	[3]			274.7	[3]
Segment, Discontinued Operations
Segment Information
Net written premiums	(0.1)		0.8
Securities reclassified to assets held for sale	222.2				236.3
Earned premiums	(0.1)		0.9
Loss and loss adjustment expense	0		0
Policy acquisition expenses	(0.7)		(0.1)
Segment Information, Additional Disclosure
Unpaid loss and loss adjustment expense reserves	$ 1,850.9				$ 1,930.0

[1] Standard & Poor's ratings as detailed above are "AA" (Very strong), "A" (Strong) and "BBB+" (Adequate).

[2] Underwriting ratios are used to measure the components of underwriting profitability and include: The loss and LAE ratio, calculated by dividing loss and LAE by earned premiums; the expense ratio, calculated by dividing policy acquisition and other underwriting expenses by earned premiums; and the combined ratio, the sum of the loss and LAE ratio and the expense ratio.

[3] As described in Note 2, balances related to the the Runoff Business are presented as held for sale. Total investment securities excludes $222.2 million and $236.3 million of fixed maturity investments reclassified to assets held for sale as of March 31, 2014 and December 31, 2013, respectively.