Fair Value Measurements - Trust Assets Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	$ 226	$ 226
Fair Value Measurements Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	226	226
Assets measured at fair value on a recurring basis	116	316
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value Measurements Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	0	0
Assets measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value Measurements Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	0	0
Assets measured at fair value on a recurring basis	116	316
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	226
Significant Unobservable Inputs (Level 3) [Member] | Fair Value Measurements Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis / Liquidation Value	226	226
Assets measured at fair value on a recurring basis	$ 0	$ 0