Fair Value Measurements - Trust Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring	$ 2,421
Assets Held for Sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring	2,421
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets Held for Sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring
Significant Other Observable Inputs (Level 2) [Member] | Assets Held for Sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring	2,421
Significant Unobservable Inputs (Level 3) [Member] | Assets Held for Sale [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value disclosure, nonrecurring	$ 2,421