Fresh Start Accounting - Assets and Liabilities at Fair Value (Parenthetical) (Detail) (USD $)	6 Months Ended					1 Months Ended	3 Months Ended
	Mar. 19, 2012	Dec. 31, 2012	Mar. 19, 2012 Reorganization Adjustments [Member]	Dec. 31, 2012 Successor [Member]	Mar. 19, 2012 Successor [Member]	Mar. 19, 2012 Predecessor [Member]	Mar. 19, 2012 Predecessor [Member]	Dec. 31, 2011 Predecessor [Member]	Mar. 19, 2012 Fair Value Adjustments [Member]	Mar. 19, 2012 WMMRC [Member]	Mar. 19, 2012 Runoff Notes [Member]
Fresh-Start Adjustment [Line Items]
Common stock, par value		$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 1.00000	$ 1
Common stock, shares authorized		500,000,000	500,000,000	500,000,000	500,000,000
Common stock, shares outstanding		201,156,078	200,000,000	201,156,078	200,000,000	1,000	1,000	1,000	1,000
Common stock, shares issued		201,156,078	200,000,000	201,156,078	200,000,000	1,000	1,000	1,000	1,000
Common stock, shares issued		201,156,078	200,000,000	201,156,078	200,000,000	1,000	1,000	1,000	1,000
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
Common stock, par value		$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 0.00001	$ 1.00000	$ 1
Common stock, shares outstanding		201,156,078	200,000,000	201,156,078	200,000,000	1,000	1,000	1,000	1,000
Common stock, shares issued		201,156,078	200,000,000	201,156,078	200,000,000	1,000	1,000	1,000	1,000
Net assets or equity Value										171,600,000
Loss contract fair market value reserve	63,100,000	63,100,000		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%