Derivatives - Fair Value Measurements on Recurring Basis (Detail) (Series F Agreement [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value On Recurring Basis [Line Items]
Fair Value of Liabilities	$ (537)	$ (826)
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value On Recurring Basis [Line Items]
Fair Value of Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value On Recurring Basis [Line Items]
Fair Value of Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Unobservable Inputs (Level 3) [Member]
Fair Value On Recurring Basis [Line Items]
Fair Value of Liabilities	$ (537)	$ (826)