VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts, Service Credits and Other
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the Beginning of the Period	$ 1,056	$ 1,286	$ 1,300
Additions	1,035	761	1,290
Write-offs	(1,026)	(991)	(1,304)
Balance at the End of the Period	1,065	1,056	1,286
Deferred Income Tax Asset Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the Beginning of the Period	0	50,031	114,190
Additions	0	0	0
Write-offs	0	(50,031)	(64,159)
Balance at the End of the Period	$ 0	$ 0	$ 50,031