CASH AND CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS; OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Thousands			12 Months Ended
	Feb. 12, 2016	Dec. 23, 2015	Dec. 31, 2015	Dec. 31, 2014
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Other				$ 10
Total cash and cash equivalents			$ 209,787	6,136
Short-term investments				26,000
Net proceeds from sale of discontinued operations (Note 3)			98,868
UTH
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Net proceeds from sale of discontinued operations (Note 3)	$ 42,500
CTC Investments | UTH
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Percentage interest sold		75.00%
Net proceeds from sale of discontinued operations (Note 3)	$ 42,500	$ 150,500
Consideration held back		$ 50,000
Ruble-denominated deposits
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Bank accounts			97	1,065
US dollar-denominated deposits
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Bank accounts			$ 209,690	5,061
Short-term investments				$ 26,000
Minimum
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Deposits in banks with original maturity period for classification as short-term investments			91 days
Maximum
CASH AND CASH EQUIVALENTS AND SHORT TERM INVESTMENTS; RECEIVABLE FROM UTH AND OTHER NON CURRENT ASSETS
Deposits in banks with original maturity period for classification as short-term investments			365 days