Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
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	$ 5,000,000	$ 18,600,000	$ 4,969,000	$ 23,778,000
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] \| 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

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

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26853-111562

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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