Derivatives - Fair Value Measurements on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014
Fair Value On Recurring Basis [Line Items]
Group II Swaps	$ 2,237
Group I Swaps	(3,142)
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value On Recurring Basis [Line Items]
Group II Swaps	0
Group I Swaps	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value On Recurring Basis [Line Items]
Group II Swaps	2,237
Group I Swaps	(3,142)
Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Fair Value On Recurring Basis [Line Items]
Group II Swaps	0
Group I Swaps	$ 0