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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - SALES TAX ACCOUNTING (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Jan. 01, 2017
Principal Transaction Revenue [Line Items]
Sales tax	$ 5.9	$ 6.6	$ 37.8	$ 34.7
NEW JERSEY
Principal Transaction Revenue [Line Items]
State sales tax, percent		7.00%		7.00%	6.625%	6.875%