CASH AND CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS; BANK OVERDRAFT (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	6 Months Ended								6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2011	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2012 Ruble-denominated deposits	Dec. 31, 2011 Ruble-denominated deposits	Jun. 30, 2012 US dollar-denominated deposits	Dec. 31, 2011 US dollar-denominated deposits	Jun. 30, 2012 Low end of range	Jun. 30, 2012 Low end of range Ruble-denominated deposits	Dec. 31, 2011 Low end of range Ruble-denominated deposits	Jun. 30, 2012 Low end of range US dollar-denominated deposits	Dec. 31, 2011 Low end of range US dollar-denominated deposits	Jun. 30, 2012 High end of range	Jun. 30, 2012 High end of range Ruble-denominated deposits	Dec. 31, 2011 High end of range Ruble-denominated deposits	Jun. 30, 2012 High end of range US dollar-denominated deposits	Dec. 31, 2011 High end of range US dollar-denominated deposits
CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS
Deposits in banks with original maturity period for classification as short-term investments										91 days					365 days
Bank accounts						$ 19,930	$ 6,434	$ 4,403	$ 4,479
Other		1,475	1,418
Cash and cash equivalents (Note 4)		25,808	12,331	34,521	59,565
Short-term investments		98,355	117,233			87,407	102,068	10,948	15,165
Annual interest rate (as a percent)											5.50%	4.10%	2.40%	2.10%		8.01%	8.70%	2.60%	2.20%
Annual interest (as a percent)	7.20%
Credit limit under overdraft agreement	34,000	30,000
Overdraft position			$ 16,941
Variable interest rate basis		Mosprime rate
Variable interest rate (as a percent)		2.21%