COMMITMENTS AND CONTINGENCIES (Narrative) (Details) $ in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2019 CAD ($) action stockholder	Sep. 30, 2019 USD ($) stockholder	Jun. 30, 2019 CAD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) action
Commitment And Contingencies [Line Items]
Purchase commitments | $					$ 586.7
Outstanding letters of credit | $					$ 8.6
Number of stockholders, filed complaints | stockholder	3	3
Commitment for telecom services 2 year period [Member]
Commitment And Contingencies [Line Items]
Other commitments	$ 83.0	$ 62.7	$ 127.0	$ 95.9
Other commitments period			2 years	2 years
Commitment for telecom services 3 year period [Member]
Commitment And Contingencies [Line Items]
Other commitments	$ 22.2	$ 16.8	$ 40.0	$ 30.2
Other commitments period			3 years	3 years
District Court of Delaware [Member]
Commitment And Contingencies [Line Items]
Number of actions pending	4				4
District Court of Colorado [Member]
Commitment And Contingencies [Line Items]
Number of actions pending	1				1
District Court of Boulder County [Member]
Commitment And Contingencies [Line Items]
Number of actions pending	1				1
Credit Letter Agreement [Member]
Commitment And Contingencies [Line Items]
Outstanding letters of credit	$ 2.8				$ 2.1
Unsecured credit agreement	$ 5.0				$ 3.8