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

Long term investment 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

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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

Fair value portion of notes payable.

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- Definition

Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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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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Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Oct. 05, 2015
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment			2 years
Weighted average maturity term for debt securities investment (or less)			1 year
Available-for-sale securities, sold	$ 0	$ 11,963,000	$ 0	$ 11,963,000
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	$ 250,000,000.0		$ 250,000,000.0
Senior Notes \| 7.75% Senior Secured Notes Due October 2020
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate						7.75%
Minimum cash and investments in marketable securities to be maintained						$ 60,000,000.0
Senior Notes \| 7.75% Senior Secured Notes Due October 2020 \| Level 3
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate	7.75%		7.75%
Senior secured notes, principal amount	$ 250,000,000.0		$ 250,000,000.0
Senior notes, fair value	$ 254,100,000		$ 254,100,000
Senior Notes \| 7.75% Senior Secured Notes Redemption Date Before October 5, 2019 \| Level 3
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount			102.00%
Senior Notes \| 7.75% Senior Secured Notes Redemption Date After October 5, 2019 \| Level 3
Cash and Investments in Marketable Securities [Line Items]
Debt redemption price percentage of principal amount			100.00%
Minimum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period			1 year		1 year
Maximum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period			2 years		2 years