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	Jun. 30, 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	$ 2,241,382
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
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	293,306	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	370,024	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	0	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	2,686	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	2,334	2,869
Standard & Poor's, B Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,909,732
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
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	68,194
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
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	255,505	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	291,532	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, B Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	615,231
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
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] | 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] | 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	37,801	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	78,492	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	0	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, B Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	116,293
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
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	2,173,188
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
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	2,686	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	2,334	2,869
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	2,178,208
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
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] | 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] | 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, 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, BB- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors