Annual report pursuant to Section 13 and 15(d)

SENIOR NOTES, NET - Schedule of Senior and Convertible Senior Notes (Descriptors) (Details)

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SENIOR NOTES, NET - Schedule of Senior and Convertible Senior Notes (Descriptors) (Details) - Senior Notes [Member] - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Jun. 30, 2015
6.00% senior notes due 2025 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 200,000,000.0   $ 200,000,000.0
Debt instrument, stated rate 6.00% 6.00% 6.00%
Unamortized premium   $ 0  
Senior Notes Due Two Thousand Twenty Five, Combined Amount [Member]      
Debt Instrument [Line Items]      
Aggregate Principal $ 400,000,000.0    
Debt instrument, stated rate 6.00% 6.00%  
Unamortized premium $ 3,614,000 $ 4,432,000