Cash and Investments in Marketable Securities [Line Items]

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- Definition

Debt investment maturity date description.

+ References

No definition available.

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- Definition

Debt investment maximum maturity period.

+ References

No definition available.

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- Definition

Minimum cash and investments in marketable securities to be maintained.

+ References

No definition available.

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- Definition

Senior notes fair value.

+ References

No definition available.

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- Definition

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

+ References

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-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Description of debt redemption features under terms of the debt agreement.

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- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

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- Definition

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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- Definition

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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment			Two years or less
Weighted average maturity term for debt securities investment			One year or less
Available-for-sale securities, sold	$ 0	$ 0	$ 11,963,000	$ 8,823,000
Senior secured notes, maturity date			Oct. 05, 2020
Level 1 to level 2 transfers	0	0	$ 0	0
Level 2 to level 1 transfers	0	$ 0	0	$ 0
Senior secured notes, principal amount	$ 250,000,000		$ 250,000,000
Senior Notes [Member] \| Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt instrument redemption terms			We may redeem some or all of these notes at a redemption price equal to 104% of the principal amount of the notes if the redemption date is prior to October 5, 2018, 102% of the principal amount of the notes if the redemption date is prior to October 5, 2019, or 100% of the principal amount of the notes if the redemption date is on or after October 5, 2019, plus, in each case, accrued and unpaid interest to the applicable redemption date.
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate	7.75%		7.75%
Senior secured notes, maturity date			Oct. 05, 2020
Minimum cash and investments in marketable securities to be maintained	$ 60,000,000		$ 60,000,000
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member] \| Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate	7.75%		7.75%
Senior secured notes, maturity date			Oct. 05, 2020
Senior secured notes, principal amount	$ 250,000,000		$ 250,000,000
Senior notes fair value	$ 259,000,000		$ 259,000,000
Senior Notes [Member] \| 7.75% Senior Secured Notes Redemption Date Before October 5, 2018 [Member] \| Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount			104.00%
Senior Notes [Member] \| 7.75% Senior Secured Notes Redemption Date Before October 5, 2019 [Member] \| Level 3 [Member]
Cash and Investments in Marketable Securities [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] \| Level 3 [Member]
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount			100.00%