FAIR VALUE MEASUREMENTS (Fair Value by Balance Sheet Grouping) (Details) - Estimate of Fair Value Measurement - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Series 2012 Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	$ 0	$ 41,450
Series 2016 Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	0	145,143
Series A 2020 Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	180,811	0
Series B 2020 Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	77,971	0
Senior Notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	696,962	731,451
Senior Notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	445,365	475,884
Senior Notes Due 2027
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	$ 428,404	$ 0