FAIR VALUE - Long-Term Debt and Convertible Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Carrying Amount | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Construction loan	$ 23,962	$ 24,866
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Construction loan	23,962	24,866
2028 Convertible notes | Carrying Amount | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	796,463	0
2028 Convertible notes | Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	1,251,085	0
2027 Convertible notes | Carrying Amount | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	506,294	483,909
2027 Convertible notes | Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	881,631	843,741
2025 Convertible notes | Carrying Amount | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	252,210	319,696
2025 Convertible notes | Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible notes	$ 494,627	$ 592,482