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Income Taxes (Valuation Allowance) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation Allowance [Line Items]
Valuation allowance	$ 146.6				$ 165.4				$ 146.6	$ 165.4
Change in valuation allowance									(9.1)	19.4	$ 35.7
Income Tax Expense (Benefit)	(23.0)	$ (6.7)	$ (6.0)	$ (9.7)	(1.0)	$ (1.6)	$ (2.2)	$ 4.6	(45.4)	(0.2)	$ (14.8)
Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	24.4								24.4
U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Valuation allowance	117.3				131.5				117.3	131.5
Net Operating Losses in Israel Subsidiaries [Member]
Valuation Allowance [Line Items]
Valuation allowance	4.6				5.5				4.6	5.5
Net Operating Losses in UK Subsidiaries [Member] [Member]
Valuation Allowance [Line Items]
Valuation allowance	0.3								0.3
Non-US | Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Change in valuation allowance										0.3
Non-US | Net Operating Losses in Israel Subsidiaries [Member]
Valuation Allowance [Line Items]
Change in valuation allowance									1.1	3.0
UNITED KINGDOM | UNITED STATES
Valuation Allowance [Line Items]
Change in valuation allowance									0.1
Subsidiaries | Luxembourg | Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance					28.3					28.3
Subsidiaries | NETHERLANDS | Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance					$ 0.1					0.1
Non-US | UNITED STATES
Valuation Allowance [Line Items]
Change in valuation allowance									2.8
Guilford Holdings, Inc. | UNITED STATES
Valuation Allowance [Line Items]
Change in valuation allowance									17.1	9.1
BAM
Valuation Allowance [Line Items]
Change in valuation allowance									3.6	6.3
Income Tax Expense (Benefit)									(11.0)	(8.7)
Houston General Insurance [Member]
Valuation Allowance [Line Items]
Change in valuation allowance									0.1	(0.5)
Star & Shield Insurance Exchange [Member]
Valuation Allowance [Line Items]
Change in valuation allowance									(6.9)	$ 1.2
Continuing Operations [Member]
Valuation Allowance [Line Items]
Change in valuation allowance									(21.4)
Stock Compensation Plan [Member]
Valuation Allowance [Line Items]
Operating Loss Carryforwards	$ 9.9								$ 9.9

X

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
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