Fair Value Measurements - Information about Valuation Inputs for Variable Interest Entity Assets and Liabilities Classified as Level 3 (Detail)	6 Months Ended		12 Months Ended
	Jun. 30, 2013 Successor Ambac [Member] European ABS Transactions [Member]	Jun. 30, 2013 Successor Ambac [Member] US Commercial ABS transaction [Member]	Dec. 31, 2012 Predecessor Ambac [Member] European ABS Transactions [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Coupon rate	0.76%	6.98%	1.64%
Maturity	18 years 15 days	10 years 11 months 27 days	12 years 4 months 2 days
Yield	1.47%	8.74%	4.02%