Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

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No definition available.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 470
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- Definition

Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt premium.

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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.

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LONG-TERM DEBT (Details) - USD ($) $ in Thousands	Feb. 15, 2018	Oct. 10, 2017	Jun. 30, 2018	Dec. 31, 2017	Sep. 07, 2017	Feb. 16, 2017
Current and long-term debt
Principal amount outstanding, net			$ 612,353	$ 409,168
Principal amount			625,005	425,005
Unamortized debt issuance costs			11,600	8,300
6.75% senior notes due 2025
Current and long-term debt
Principal amount outstanding, net			$ 612,353	$ 409,168
Interest rate (as a percent)			6.75%	6.75%	6.75%	6.75%
Principal amount					$ 850,000	$ 850,000
Redemption price (as a percent)		103.00%
Unamortized discount			$ 7,700	$ 8,100
Unamortized debt issuance costs			10,700	$ 7,700
Additional 2025 Notes
Current and long-term debt
Principal amount	$ 200,000
Redemption price (as a percent)	103.00%
Unamortized premium related to debt issued			$ 5,700