Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Successor Ambac [Member]	Mar. 31, 2013 Predecessor Ambac [Member]	Mar. 31, 2014 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Successor Ambac [Member]	Mar. 31, 2013 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Predecessor Ambac [Member]	Mar. 31, 2014 Other Postretirement Benefit Plan, Defined Benefit [Member] Successor Ambac [Member]	Mar. 31, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member] Predecessor Ambac [Member]	Mar. 31, 2014 Gain (Loss) on Foreign Currency Translation [Member] Successor Ambac [Member]	Mar. 31, 2013 Gain (Loss) on Foreign Currency Translation [Member] Predecessor Ambac [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 104,417	$ 11,661	$ 11,661	$ 625,385	$ (41,910)	$ 651,272	$ 10,847	$ (5,860)	$ 42,724	$ (20,027)
Other comprehensive income before reclassifications			98,860	99,960	94,622	100,180	0	0	4,238	(220)
Amounts reclassified from accumulated other comprehensive income			(6,104)	(5,274)	(5,900)	(6,082)	(204)	808
Net current period other comprehensive income			92,756	94,686	88,722	94,098	(204)	808	4,238	(220)
Ending Balance	$ 104,417	$ 11,661	$ 104,417	$ 720,071	$ 46,812	$ 745,370	$ 10,643	$ (5,052)	$ 46,962	$ (20,247)