ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ACCOUNTS RECEIVABLE
Accounts receivable	$ 58,552	$ 58,568
Less: allowance for doubtful accounts	(15,023)	(13,149)
Total accounts receivable, net	43,529	45,419
U.S. wireless, Retail
ACCOUNTS RECEIVABLE
Accounts receivable	19,530	36,026
U.S. wireless, Wholesale
ACCOUNTS RECEIVABLE
Accounts receivable	$ 39,022	22,502
Other
ACCOUNTS RECEIVABLE
Accounts receivable		$ 40