LONG-TERM DEBT - Prepayments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017
Scenario A
Line of Credit Facility [Line Items]
Prepayment made before first anniversary, percent	2.00%
Prepayment made on and after first anniversary and prior to second anniversary, percent	1.00%
Scenario B
Line of Credit Facility [Line Items]
Prepayment made before first anniversary, percent	1.00%
Prepayment made on and after first anniversary and prior to second anniversary, percent	0.50%