Senior Secured Notes - Additional Information (Detail) - USD ($)		12 Months Ended
Oct. 05, 2015	Dec. 31, 2018
Secured Notes [Line Items]
Senior secured notes, principal amount		$ 250,000,000
Actual days outstanding		360 days
Senior secured notes, maturity date		Oct. 05, 2020
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member]
Secured Notes [Line Items]
Senior secured notes, principal amount	$ 250,000,000
Senior secured notes, interest rate	7.75%
Senior secured notes, maturity date	Oct. 05, 2020
Frequency of payment		Quarterly
Issuance costs	$ 8,900,000
Debt discount on transaction and facility fees	8,700,000
Unamortized debt discount and issuance costs		$ 3,100,000
Minimum cash and investments in marketable securities to be maintained	$ 60,000,000
Percentage of repurchase of notes on principal amount of notes	101.00%
Percentage of repurchase of notes on principal amount of notes upon sale of assets	100.00%
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member] \| Level 3 [Member]
Secured Notes [Line Items]
Senior notes fair value		$ 258,000,000
Senior Notes [Member] \| 7.75% Senior Secured Notes Redemption Date Before October 5, 2019 [Member]
Secured Notes [Line Items]
Debt redemption price percentage of principal amount	102.00%
Senior Notes [Member] \| 7.75% Senior Secured Notes Redemption Date After October 5, 2019 [Member]
Secured Notes [Line Items]
Debt redemption price percentage of principal amount	100.00%

Actual days outstanding.

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Debt discount on transaction and facility fees paid.

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Minimum cash and investments in marketable securities to be maintained.

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- Definition

Redemption price as percentage of principal amount in case of change of control.

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Redemption price as percentage of principal amount in case of sale of assets.

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- Definition

Secured notes.

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- Definition

Senior notes fair value.

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Description of the frequency of periodic payments (monthly, quarterly, annual).

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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- Definition

Percentage of principal amount of debt redeemed.

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- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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