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SHORT-TERM AND LONG-TERM DEBT - Narrative (Details)
Dec. 01, 2016
USD ($)
Dec. 31, 2017
USD ($)
joint_venture
line_of_credit
Dec. 31, 2016
USD ($)
Line of Credit Facility [Line Items]      
Total short-term debt   $ 566,000,000 $ 513,000,000
Number of consolidated real estate joint ventures | joint_venture   2  
Revolver | Alliance Bernstein      
Line of Credit Facility [Line Items]      
Maximum borrowing capacity $ 200,000,000    
Debt instrument, term 364 days    
Line of credit facility, amount outstanding   $ 75,000,000  
Debt instrument, interest rate, stated percentage   2.40%  
Revolver | Commercial Banks and Other Lenders | Alliance Bernstein      
Line of Credit Facility [Line Items]      
Maximum borrowing capacity   $ 1,000,000,000  
Line of credit facility, amount outstanding   0  
Incremental amount in principal allowed (up to)   250,000,000  
Revolver | Commercial Paper | Alliance Bernstein      
Line of Credit Facility [Line Items]      
Maximum borrowing capacity   $ 1,000,000,000  
Line of Credit | Financial Institutions      
Line of Credit Facility [Line Items]      
Number of uncommitted lines of credit | line_of_credit   4  
Line of Credit | Financial Institutions | Alliance Bernstein      
Line of Credit Facility [Line Items]      
Number of uncommitted lines of credit | line_of_credit   3  
Line of Credit | Financial Institutions | SCB LLC      
Line of Credit Facility [Line Items]      
Line of credit facility, amount outstanding   $ 0  
Incremental amount in principal allowed (up to)   $ 175,000,000  
Number of uncommitted lines of credit | line_of_credit   3  
Number of lines of credit with aggregate borrowing capacity | line_of_credit   2  
Number of lines of credit with no stated credit limit | line_of_credit   1  
Commercial Paper      
Line of Credit Facility [Line Items]      
Debt instrument, interest rate, stated percentage   1.60% 0.90%
Total short-term debt   $ 491,000,000 $ 513,000,000
Mortgage loans on real estate | 4.1% Non-recourse mortgage debt      
Line of Credit Facility [Line Items]      
Debt instrument, interest rate, stated percentage   4.10%  
Long-term debt   $ 82,000,000 0
Mortgage loans on real estate | 3.9% Non-recourse mortgage debt      
Line of Credit Facility [Line Items]      
Debt instrument, interest rate, stated percentage   3.90%  
Long-term debt   $ 121,000,000 $ 0