Derivatives - Fair Value Measurements on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
Fair Value on Recurring Basis [Line Items]
Group I Swaps	$ (8,735)
Group II Swaps	(12,990)
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value on Recurring Basis [Line Items]
Group I Swaps	0
Group II Swaps	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value on Recurring Basis [Line Items]
Group I Swaps	(8,735)
Group II Swaps	(12,990)
Fair Value, Measurements, Recurring | Unobservable Inputs (Level 3)
Fair Value on Recurring Basis [Line Items]
Group I Swaps	0
Group II Swaps	$ 0