Fair Value Measurements - Trust's Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Detail) (Non-Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, nonrecurring	$ 22,826
Investments in Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, nonrecurring	22,826
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, nonrecurring	22,826
Significant Unobservable Inputs (Level 3) [Member] | Investments in Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, nonrecurring	$ 22,826