Schedule of Related Party Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Principal amount	$ 129,200
Net carrying amount	72,196	$ 79,666
Related Party Debt
Related Party Transaction [Line Items]
Principal amount	71,506	79,666
Unamortized premium	758
Unaccreted debt issuance costs	(68)
Net carrying amount	$ 72,196	$ 79,666

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

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Amount, after accumulated amortization, of debt premium.

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The amount for notes payable (written promise to pay), payable to related parties, which are due after one year (or one business cycle).

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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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