STOCKHOLDERS' EQUITY (Details) (USD $)	1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 31, 2013	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 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	450,410			1,503,505
At-the-market equity offering program, proceeds from sale of stock during period	27,900,000		23,700,000	106,100,000
At-the-market equity offering program, payments of stock issuance costs during period	400,000			1,600,000
At-the-market equity offering program, remaining authorized offering amount			642,300,000	642,300,000
Accumulated Other Comprehensive Income
Foreign currency translation			20,293,000	20,293,000	23,441,000
Unrealized gain on marketable debt securities			(208,000)	(208,000)	807,000
Other			1,208,000	1,208,000	(894,000)
Total accumulated other comprehensive income			$ 21,293,000	$ 21,293,000	$ 23,354,000