STOCKHOLDERS' EQUITY (Details) (USD $)	1 Months Ended	3 Months Ended	6 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Jun. 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			1,128,700
At-the-market equity offering program, proceeds from sale of stock during period		77,300,000	82,400,000
At-the-market equity offering program, payments of stock issuance costs during period			1,300,000
At-the-market equity offering program, remaining authorized offering amount		666,300,000	666,300,000
Accumulated Other Comprehensive Income
Foreign currency translation		18,628,000	18,628,000	23,441,000
Unrealized gain on marketable debt securities		0	0	807,000
Other		1,124,000	1,124,000	(894,000)
Total accumulated other comprehensive income		$ 19,752,000	$ 19,752,000	$ 23,354,000