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
 9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Unrealized losses forecasted to be included in earnings transferred from AOCI in the next twelve months $ 0.6  
Level 2 [Member] | Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed rate mortgages, fair value disclosure $ 285.0 $ 214.0
Weighted average market interest rate 3.94% 3.89%
Weighted average contractual interest rate 4.87% 5.25%
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Notional amount $ 595.0 $ 425.0
Weighted average remaining term 3 years 9 months  
Weighted average fixed rate 1.51%  
Reported Value Measurement [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fixed rate mortgages, fair value disclosure $ 272.7 $ 201.7