Municipal Bond Guarantee (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2014 BAM Contract	Sep. 30, 2014 BAM Y Contract	Dec. 31, 2013 BAM Contract	Jul. 31, 2012 HG Global	Sep. 30, 2014 HG Global	Sep. 30, 2013 HG Global	Sep. 30, 2014 HG Global	Sep. 30, 2013 HG Global	Sep. 30, 2014 HG Global Preferred Stock	Sep. 30, 2014 HG Global Common Stock	Sep. 30, 2014 Build America Mutual	Sep. 30, 2013 Build America Mutual	Sep. 30, 2014 Build America Mutual	Sep. 30, 2013 Build America Mutual	Sep. 30, 2014 HG Re	Jul. 31, 2012 BAM Management	Sep. 30, 2014 Surplus Note BAM	Sep. 30, 2014 Fixed interest rate Surplus Note BAM	Sep. 30, 2014 Variable Rate Surplus Note BAM	Sep. 30, 2014 Combination One Surplus Note BAM Y	Sep. 30, 2014 Combination Two Surplus Note BAM Y	Sep. 30, 2014 Financial Guarantee [Member]
Guarantor Obligations [Line Items]
basis points																	3.00%
Municipal bond contract	1,431	1,431	701
Insured Financial Obligations, Remaining Weighted Average Contract Period		12 years 11 months 0 days	13 years 9 months 21 days
Municipal bond outstanding principal	$ 9,963.6	$ 9,963.6	$ 4,703.7
Municipal bond outstanding interest	5,945.5	5,945.5	3,264.4
Municipal bond debt service outstanding	15,909.1	15,909.1	7,968.1
Partners Capital Contribution				594.5												14.5
Ownership interest (as a percent)									96.90%	88.40%
Surplus Notes				503.0
Statutory Accounting Practices, Statutory Capital and Surplus, Balance															445.7
Percentage of par value of policy reinsured																						15.00%
Income (Loss) from Continuing Operations before Income Taxes, Domestic					3.8	10.5	13.4	28.2			(13.1)	(15.1)	(29.7)	(60.2)
Interest income (expense), surplus notes	3.9	11.8				10.1		30.2			(3.9)	(10.1)	(11.8)	(30.2)
Number of years of change in interest rate																				5	3
Financial Guarantee Insurance Contracts, Unearned Premium Revenue	$ 23.4	$ 23.4	$ 13.2
Debt Instrument, Interest Rate, Stated Percentage																		8.00%	3.13%
Year of U.S. Treasury Rate		1