Investments - Summary of Amounts Included in Net Realized Gains and Other-Than-Temporary Impairments (Detail) (USD $) In Thousands, unless otherwise specified	2 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended
Jun. 30, 2013 Successor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]
Change In Net Unrealized Gains And Losses From Investment Securities [Line Items]
Gross realized gains on securities	$ 16,612	$ 5,870	$ 67,681	$ 47,448	$ 68,505
Gross realized losses on securities	(1,592)	(2)	(570)	(320)	(891)
Foreign exchange gains	3,452	1,377	(44)	6,177	(155)
Net realized gains	18,472	7,245	67,067	53,305	67,459
Net other-than-temporary impairments	$ (2,002)	$ (467)	$ (2,328)	$ (467)	$ (5,399)

The aggregate foreign currency transaction gain (loss) (both realized and unrealized) included in determining net income for the reporting period. Excludes foreign currency transactions designated as hedges of net investment in a foreign entity and intercompany foreign currency transactions that are of a long-term nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements. For certain enterprises, primarily banks, that are dealers in foreign exchange, foreign currency transaction gains (losses) may be disclosed as dealer gains (losses).

+ References+ Details

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

+ References+ Details