FAIR VALUE MEASUREMENTS (Fair Value by Balance Sheet Grouping) (Details) - Estimate of Fair Value Measurement - USD ($) $ in Thousands	Jun. 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	177,964	0
Series B 2020 Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	78,756	0
Senior Notes due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	674,324	731,451
Senior Notes due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable, fair value disclosure	$ 407,462	$ 475,884