FAIR VALUE OF FINANCIAL INSTRUMENTS - Carrying Amount and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Secured notes payable, net | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 162,159	$ 182,572
Unsecured term loans, net | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	248,741	248,765
Unsecured senior guaranteed notes, net | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	946,784	797,098
Unsecured line of credit, net | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	62,337
Fair Value, Inputs, Level 2 | Secured notes payable, net | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	168,010	183,253
Fair Value, Inputs, Level 2 | Unsecured term loans, net | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	250,000	250,000
Fair Value, Inputs, Level 2 | Unsecured senior guaranteed notes, net | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	987,588	790,267
Fair Value, Inputs, Level 2 | Unsecured line of credit, net | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 0	$ 64,000