USE OF DERIVATIVES, OFFSETTING DISCLOSURES AND CHANGES IN OTHER COMPREHENSIVE INCOME BY COMPONENT - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Sep. 30, 2016
Derivative Instruments And Hedging Activities Disclosures [Line Items]
SWAP agreement notional amount during period	$ 700	$ 1,200	$ 100
SWAP agreement average interest rate during period	2.75%	2.62%	4.09%
Swap agreement notional amount expiring during period	$ 600	$ 2,300
SWAP agreement average interest rate expiring during period	0.79%	0.77%
Interest Rate Swap Agreements [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Payment term of LIBOR interest rate agreement		20 years
Interest Rate Swap Agreements [Member] | Minimum [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Payment term of LIBOR interest rate agreement		2 years
Interest Rate Swap Agreements [Member] | Maximum [Member]
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Payment term of LIBOR interest rate agreement		3 years