Derivatives - Fair Value Measurements on Recurring Basis (Detail) $ in Thousands	Sep. 30, 2015 USD ($)
Group I Swaps
Fair Value on Recurring Basis [Line Items]
Swaps	$ (10,148)
Group I Swaps | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value on Recurring Basis [Line Items]
Swaps	0
Group I Swaps | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value on Recurring Basis [Line Items]
Swaps	(10,148)
Group I Swaps | Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Fair Value on Recurring Basis [Line Items]
Swaps	0
Group II Swaps
Fair Value on Recurring Basis [Line Items]
Swaps	(4,322)
Group II Swaps | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value on Recurring Basis [Line Items]
Swaps	0
Group II Swaps | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value on Recurring Basis [Line Items]
Swaps	(4,322)
Group II Swaps | Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Fair Value on Recurring Basis [Line Items]
Swaps	$ 0