Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified			1 Months Ended	4 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	4 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	4 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	4 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Apr. 30, 2013 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2013 Successor [Member]	Jun. 30, 2014 Successor [Member]	Jun. 30, 2014 Successor [Member]	Apr. 30, 2013 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Predecessor Ambac [Member]	Apr. 30, 2013 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Predecessor Ambac [Member]	Jun. 30, 2013 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Successor [Member]	Jun. 30, 2014 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Successor [Member]	Jun. 30, 2014 Unrealized Gains (Losses) on Available-for-Sale Securities [Member] Successor [Member]	Apr. 30, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member] Predecessor Ambac [Member]	Apr. 30, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member] Predecessor Ambac [Member]	Jun. 30, 2013 Other Postretirement Benefit Plan, Defined Benefit [Member] Successor [Member]	Jun. 30, 2014 Other Postretirement Benefit Plan, Defined Benefit [Member] Successor [Member]	Jun. 30, 2014 Other Postretirement Benefit Plan, Defined Benefit [Member] Successor [Member]	Apr. 30, 2013 Accumulated Translation Adjustment [Member] Predecessor Ambac [Member]	Apr. 30, 2013 Accumulated Translation Adjustment [Member] Predecessor Ambac [Member]	Jun. 30, 2013 Accumulated Translation Adjustment [Member] Successor [Member]	Jun. 30, 2014 Accumulated Translation Adjustment [Member] Successor [Member]	Jun. 30, 2014 Accumulated Translation Adjustment [Member] Successor [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 306,328	$ 11,661	$ 720,071	$ 625,385	$ 0	$ 104,417	$ 11,661	$ 745,370	$ 651,272	$ 0	$ 46,812	$ (41,910)	$ (5,052)	$ (5,860)		$ 10,643	$ 10,847	$ (20,247)	$ (20,027)	$ 0	$ 46,962	$ 42,724
Other comprehensive income before reclassifications			88,079	188,039	(85,035)	196,431	295,291	88,516	188,696	(72,511)	179,479	274,101	0	0	0	0		(437)	(657)	(12,524)	16,952	21,190
Amounts reclassified from accumulated other comprehensive income			(7,890)	(13,164)	(18,472)	5,480	(624)	(7,267)	(13,349)	(18,472)	5,684	(216)	(623)	185	0	(204)	(408)	0
Elimination Of Predecessor Shareholder Equity And Noncontrolling Interest			(800,260)	(800,260)				(826,619)	(826,619)	0	0	0	5,675	5,675				20,684	20,684
Net current period other comprehensive income			(720,071)	(625,385)	(103,507)	201,911	294,667	(745,370)	(651,272)	(90,983)	185,163	273,885	5,052	5,860	0	(204)	(408)	20,247	20,027	(12,524)	16,952	21,190
Ending Balance	$ 306,328	$ 11,661	$ 0	$ 0	$ (103,507)	$ 306,328	$ 306,328	$ 0	$ 0	$ (90,983)	$ 231,975	$ 231,975				$ 10,439	$ 10,439	$ 0	$ 0	$ (12,524)	$ 63,914	$ 63,914