SHORT-TERM AND LONG-TERM DEBT - Schedule of Short-Term Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Outstanding short-term debt	$ 421,555	$ 386,140
Line of Credit [Member]
Short-term Debt [Line Items]
Outstanding short-term debt	16,861	16,392
Commercial Paper [Member]
Short-term Debt [Line Items]
Outstanding short-term debt	$ 404,694	$ 369,748