STOCKHOLDERS' EQUITY (Details) (USD $)	1 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Equity [Abstract]
At-the-market equity offering program, authorized amount	$ 750,000,000
At-the-market equity offering program, shares issued during period		72,300
At-the-market equity offering program, proceeds from sale of stock during period		5,100,000
At-the-market equity offering program, payments of stock issuance costs during period		100,000
At-the-market equity offering program, remaining authorized offering amount	744,800,000	744,800,000
Accumulated Other Comprehensive Income
Foreign currency translation	21,350,000	21,350,000	23,441,000
Unrealized gain on marketable debt securities	868,000	868,000	807,000
Other	(390,000)	(390,000)	(894,000)
Total accumulated other comprehensive income	$ 21,828,000	$ 21,828,000	$ 23,354,000