Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS - Narrative (Details)

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FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Unrealized gains forecasted to be included in earnings transferred from AOCI in the next twelve months $ 4.5  
Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed rate mortgages, fair value disclosure $ 279.1 $ 282.6
Weighted average market interest rate 4.39% 4.04%
Weighted average contractual interest rate 4.85% 4.87%
Designated as Hedging Instrument | Interest Rate Swap    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notional amount $ 720.0 $ 595.0
Weighted average remaining term 4 years 5 months  
Weighted average fixed rate 1.77%  
Reported Value Measurement    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed rate mortgages, fair value disclosure $ 273.3 $ 271.5