LONG-TERM DEBT - Annual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Annual maturities of total debt adjusted for debt issuance costs, discounts and premiums
2020	$ 81,555
2021	87,697
2022	93,143
2023	73,184
2024	306,157
Thereafter	2,503,170
Total debt adjusted for debt issuance costs, discounts and premiums	3,144,906	$ 3,205,058
First Mortgage Bonds, Series 2014E-1, 3.70% due 2024
Annual maturities of total debt adjusted for debt issuance costs, discounts and premiums
2024	$ 250,000

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
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-Section 50
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