DEBT - Narrative (Details) - Revolving Credit Facility - USD ($)	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Long-term line of credit, maximum borrowing capacity	$ 1,395,000,000
Long-term line of credit	850,000,000
Long-term line of credit, remaining borrowing capacity	$ 545,000,000
Weighted average interest rate (percent)	4.90%
Interest costs capitalized	$ 5,400,000	$ 5,000,000
Revolving Credit Facility, Maturing May 2019
Line of Credit Facility [Line Items]
Long-term line of credit, maximum borrowing capacity	1,120,000,000
Revolving Credit Facility, Maturing May 2018
Line of Credit Facility [Line Items]
Long-term line of credit, maximum borrowing capacity	$ 275,000,000