BUSINESS AND BASIS OF PRESENTATION (Details) - shares shares in Millions	3 Months Ended	6 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Basis Of Presentation And Significant Accounting Policies [Line Items]
Weighted-average shares included to account for the dilutive effect of the Part A and Part B RSUs	1.9	2.5	2.3	2.0
Allstream
Basis Of Presentation And Significant Accounting Policies [Line Items]
Percentage of entity acquired	100.00%		100.00%

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 28A
-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1500-109256

Name:	us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration