Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail) (Successor Ambac [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Standard & Poor's, CCC Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 2,117,282
Weighted Average Underlying Rating, AA- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	438,140
Standard & Poor's, A+ Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		570,394
Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	391,457	449,555
Weighted Average Underlying Rating, BBB- Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	17,436	17,444
Weighted Average Underlying Rating, D Rating [Member] | Assured Guaranty Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,816	2,917
Weighted Average Underlying Rating, D Rating [Member] | Financial Guarantee Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,755	2,869
Standard & Poor's, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		2,855,058
Standard & Poor's, B+ Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,969,886
Standard & Poor's, CCC+ Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		1,811,879
Municipal Bonds [Member] | Standard & Poor's, CCC Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	66,002
Municipal Bonds [Member] | Weighted Average Underlying Rating, AA- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	400,268
Municipal Bonds [Member] | Standard & Poor's, A+ Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		532,752
Municipal Bonds [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	312,622	372,392
Municipal Bonds [Member] | Weighted Average Underlying Rating, BBB- Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Municipal Bonds [Member] | Weighted Average Underlying Rating, D Rating [Member] | Assured Guaranty Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Municipal Bonds [Member] | Weighted Average Underlying Rating, D Rating [Member] | Financial Guarantee Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Municipal Bonds [Member] | Standard & Poor's, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		969,740
Municipal Bonds [Member] | Standard & Poor's, B+ Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	778,892
Municipal Bonds [Member] | Standard & Poor's, CCC+ Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		64,596
Corporate Debt Securities [Member] | Standard & Poor's, CCC Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Corporate Debt Securities [Member] | Weighted Average Underlying Rating, AA- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	37,872
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		37,642
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	78,835	77,163
Corporate Debt Securities [Member] | Weighted Average Underlying Rating, BBB- Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	17,436	17,444
Corporate Debt Securities [Member] | Weighted Average Underlying Rating, D Rating [Member] | Assured Guaranty Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Corporate Debt Securities [Member] | Weighted Average Underlying Rating, D Rating [Member] | Financial Guarantee Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Corporate Debt Securities [Member] | Standard & Poor's, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		132,249
Corporate Debt Securities [Member] | Standard & Poor's, B+ Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	134,143
Corporate Debt Securities [Member] | Standard & Poor's, CCC+ Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,051,280
Mortgage and Asset-Backed Securities [Member] | Weighted Average Underlying Rating, AA- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, A+ Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Mortgage and Asset-Backed Securities [Member] | Weighted Average Underlying Rating, BBB- Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Mortgage and Asset-Backed Securities [Member] | Weighted Average Underlying Rating, D Rating [Member] | Assured Guaranty Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,816	2,917
Mortgage and Asset-Backed Securities [Member] | Weighted Average Underlying Rating, D Rating [Member] | Financial Guarantee Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,755	2,869
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		1,753,069
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, B+ Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,056,851
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC+ Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		1,747,283
Short-Term [Member] | Standard & Poor's, CCC Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Weighted Average Underlying Rating, AA- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Standard & Poor's, A+ Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Weighted Average Underlying Rating, BBB- Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Weighted Average Underlying Rating, D Rating [Member] | Assured Guaranty Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Weighted Average Underlying Rating, D Rating [Member] | Financial Guarantee Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Standard & Poor's, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Standard & Poor's, B+ Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors
Short-Term [Member] | Standard & Poor's, CCC+ Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors