Financial Guarantees in Force - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Guarantor Obligations [Line Items]
Gross par amount of financial guarantees outstanding	$ 86,373,000	$ 119,235,000
Net par amount of financial guarantees	79,346,000	108,299,000
Gross financial guarantees in force	137,745,000	188,853,000
Net financial guarantees in force	$ 126,306,000	171,000,000
Highest single insured risk of aggregate net par amount guaranteed	2.10%
California [Member]
Guarantor Obligations [Line Items]
Aggregate net par amounts in force	13.00%
New York [Member]
Guarantor Obligations [Line Items]
Aggregate net par amounts in force	5.40%
No other state [Member] | Maximum [Member]
Guarantor Obligations [Line Items]
Aggregate net par amounts in force	5.00%
Successor [Member]
Guarantor Obligations [Line Items]
Financial Guarantee Insurance Contracts, Accelerated Premium Revenue, Amount	$ 52,416	$ 137,400	$ 29,964