Schedule of Outstanding Debt (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Equipment Notes	$ 53,316	$ 8,246
Less current portion	(11,559)	(1,771)
Total long-term debt	41,757	6,475
Secured long-term debt	53,316	8,246
Secured Equipment Notes due in September 2019 with Monthly Payments of $329,718 [Member]
Debt Instrument [Line Items]
Equipment Notes	18,739
Secured Equipment Notes due in September 2019 with Monthly Payments of $90,939 [Member]
Debt Instrument [Line Items]
Equipment Notes	5,168
Secured Equipment Notes due in February 2019 [Member]
Debt Instrument [Line Items]
Equipment Notes	22,488
Secured Equipment Notes due in June 2018 [Member]
Debt Instrument [Line Items]
Equipment Notes	$ 6,921	$ 8,246

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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