Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Predecessor Ambac [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Other Postretirement Benefit Plan, Defined Benefit [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Other Postretirement Benefit Plan, Defined Benefit [Member]	Mar. 31, 2014 Successor Ambac [Member]	Mar. 31, 2014 Successor Ambac [Member] Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Mar. 31, 2014 Successor Ambac [Member] Other Postretirement Benefit Plan, Defined Benefit [Member]	Mar. 31, 2014 Successor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Mar. 31, 2014 Successor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Unrealized Gains (Losses) on Available-for-Sale Securities [Member]	Mar. 31, 2014 Successor Ambac [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Other Postretirement Benefit Plan, Defined Benefit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains		$ (6,082)						$ (5,900)
Tax (expense) benefit	657						3,249
Net of tax and noncontrolling interest		(6,082)		(5,274)				(5,900)		(6,104)
Prior service cost						1,707						(166)
Actuarial gains (losses)						(899)						(38)
Total before tax						808						(204)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (5,274)	$ (6,082)	$ 808			$ (808)	$ (6,104)	$ (5,900)	$ (204)			$ 204