Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Assets and Liability Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Liabilities:
Derivative liability	$ 6,100us-gaap_DerivativeLiabilities	$ 7,519us-gaap_DerivativeLiabilities	$ 13,529us-gaap_DerivativeLiabilities	$ 17,994us-gaap_DerivativeLiabilities
Long-term debt derivative liabilities	6,100us-gaap_DerivativeLiabilitiesNoncurrent	7,400us-gaap_DerivativeLiabilitiesNoncurrent
Fair Value, Measurements, Recurring
Asset:
Cash equivalents-money markets	40,163	65,156
Liabilities:
Long-term debt derivative liabilities	6,100	7,400
Fair Value, Measurements, Recurring \| Warrant
Liabilities:
Derivative liability		119
Fair Value, Measurements, Recurring \| Level 1
Asset:
Cash equivalents-money markets	40,163	65,156
Fair Value, Measurements, Recurring \| Level 3
Liabilities:
Long-term debt derivative liabilities	6,100	7,400
Fair Value, Measurements, Recurring \| Level 3 \| Warrant
Liabilities:
Derivative liability		$ 119