Fresh Start Accounting - Adjustment Reflects Reduction of Equity Value Resulting from Fresh Start Accounting (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Mar. 19, 2012
Fresh-Start Adjustment [Line Items]
Fair market value reduction			$ 8,400
Elimination of Court assigned value related to NOLs			70,000
Total change in fair market value affecting Equity Value			78,400
Court assigned Equity Value recorded as additional paid-in capital			154,998
Additional paid-in capital at March 19, 2012	106,628	77,142	76,598
WMMRC [Member]
Fresh-Start Adjustment [Line Items]
Fair market value of WMMRC (Court assigned)			140,000
Fair market value of WMMRC			131,600
Fair market value reduction			$ 8,400