Fresh Start Financial Statement Reporting - Additional Information (Detail)	1 Months Ended
	Apr. 30, 2013 USD ($)
Fresh-Start Adjustment [Line Items]
Enterprise value	$ 185,000,000
Allocated amount of Net Operating Loss (NOL)	3,650,000,000
Tax credits carried forward	60,000,000
Upfront cash	30,000,000
Other operating payments	15,000,000
Junior Surplus Notes To Be Issued	$ 350,000,000
Interest on junior surplus notes	5.10%
Minimum [Member]
Fresh-Start Adjustment [Line Items]
Discount rate	12.00%
Capital investment	$ 135,000,000
Rate of return on investment	6.00%
Discount rate of investment	25.00%
Maximum [Member]
Fresh-Start Adjustment [Line Items]
Discount rate	17.00%
Capital investment	$ 190,000,000
Rate of return on investment	8.00%
Discount rate of investment	35.00%
Ambac Assurance [Member]
Fresh-Start Adjustment [Line Items]
Maximum Reimbursement Of Operating Expenses	$ 5,000,000
Surplus Notes [Member]
Fresh-Start Adjustment [Line Items]
Discount rate	10.60%
Two Thousand And Seventeen [Member] | Ambac Assurance [Member]
Fresh-Start Adjustment [Line Items]
Maximum Reimbursement Of Operating Expenses after 2017	$ 4,000,000