Debt - Components of Long-term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 13, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal	$ 700,000		$ 630,000
Unamortized debt issuance debt costs	5,800		1,025
Long-term Debt, Current Maturities	(1,750)		(500,000)
Long-term debt	698,250		130,000
5.25% Senior Notes due March 15, 2019 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Principal	500,000		500,000
Unamortized debt issuance debt costs			260
6% Blue Torch Finance, LLC Term Loan [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Principal	70,000	$ 70,000
Unamortized debt issuance debt costs	5,254
6% Related Party Term Loan [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Principal	130,000		130,000
Unamortized debt issuance debt costs	$ 546		$ 765

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

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