FAIR VALUE MEASUREMENT (Tables)

12 Months Ended

Dec. 31, 2011

FAIR VALUE MEASUREMENT

Financial assets and liabilities measured at fair value within the fair value hierarchy

	Total		Level 1			Level 2			Level 3
Financial assets:
Cash equivalents and short-term investments	$	7,645	$	—		$	7,645	(i)	$	—
Available-for-sale securities		145,411		142,490	(ii)		2,921	(iii)		—
Trade receivables		75,899		—			75,899	(iv)		—
	$	228,955	$	142,490		$	86,465		$	—
Financial liabilities:
Fair value of derivative financial instruments(iii)	$	4,404	$	—		$	4,404		$	—

• (i)

  Fair value approximates the carrying value due to short-term nature.
  
  

  (ii)

  Recorded at fair value using quoted market prices.
  
  

  (iii)

  Recorded at fair value based on broker-dealer quotations.
  
  

  (iv)

  Trade receivables from provisional invoices for concentrate sales are included within Level 2 as they are valued using quoted forward rates derived from observable market data based on the month of expected settlement.