Fresh Start Accounting - Assets and Liabilities at Fair Value (Parenthetical) (Detail) (USD $)	6 Months Ended						1 Months Ended	3 Months Ended
	Mar. 19, 2012	Sep. 30, 2013	Dec. 31, 2012	Mar. 19, 2012 WMMRC [Member]	Mar. 19, 2012 Runoff Notes [Member]	Mar. 19, 2012 Successor [Member]	Mar. 19, 2012 Predecessor [Member]	Mar. 19, 2012 Predecessor [Member]	Mar. 19, 2012 Reorganization Adjustments [Member]	Mar. 19, 2012 Fair Value Adjustments [Member]
Fresh-Start Adjustment [Line Items]
Common stock, par value		$ 0.00001	$ 0.00001			$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 1
Common stock, shares outstanding		201,842,351	201,156,078			200,000,000	1,000	1,000	200,000,000	1,000
Common stock, shares issued		201,842,351	201,156,078			200,000,000	1,000	1,000	200,000,000	1,000
Common stock, shares authorized		500,000,000	500,000,000			500,000,000			500,000,000
Cash contributed to the Company by creditors	$ 75,000,000							$ 75,000,000
Court's valuation of WMMRC				140,000,000
Outstanding amount of notes					130,000,000
Net assets or equity Value				171,600,000
Loss contract fair market value reserve	63,100,000	51,230,000	52,217,000			63,100,000
Increase in equity value							194,700,000
Reduction in WMMRC's FMV	8,400,000			8,400,000
Value related to NOLs	$ 70,000,000
Valuation allowance	100.00%	100.00%