EQUITY AND NONCONTROLLING INTEREST (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Apr. 09, 2013	Oct. 31, 2008
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)			151,069,609
Balance at beginning of period			$ 1,287,332	$ 1,214,631
Foreign currency translation	(3,848)	(9,573)	(5,366)	(2,521)
Common stock purchases			(3,134)	(7,417)
Share-based compensation			9,393	8,444
Exercise of stock options and warrants				812
Tax benefits from share-based compensation			(1,501)	4,047
Acquisition of the 50% noncontrolling interest in Geostream (Note 3)			(13,114)
Shares surrendered				(1,006)
Net income (loss)	(3,772)	29,245	(3,958)	31,821
Balance at end of period (in shares)	152,443,492		152,443,492
Balance at end of period	1,269,652	1,248,811	1,269,652	1,248,811
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)			151,070,000	150,733,000
Balance at beginning of period			15,108	15,073
Common stock purchases (in shares)			(410,000)	(468,000)
Common stock purchases			(42)	(47)
Share-based compensation (in shares)			1,783,000	855,000
Share-based compensation			178	86
Exercise of stock options and warrants (in shares)				89,000
Exercise of stock options and warrants				9
Shares surrendered (in shares)				(68,000)
Shares surrendered				(7)
Balance at end of period (in shares)	152,443,000	151,141,000	152,443,000	151,141,000
Balance at end of period	15,244	15,114	15,244	15,114
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period			925,132	915,400
Common stock purchases			(3,092)	(7,370)
Share-based compensation			9,215	8,358
Exercise of stock options and warrants				803
Tax benefits from share-based compensation			(1,501)	4,047
Acquisition of the 50% noncontrolling interest in Geostream (Note 3)			22,432
Shares surrendered				(999)
Balance at end of period	952,186	920,239	952,186	920,239
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period			(6,148)	(58,231)
Foreign currency translation			(4,699)	(1,393)
Acquisition of the 50% noncontrolling interest in Geostream (Note 3)			(4,350)
Balance at end of period	(15,197)	(59,624)	(15,197)	(59,624)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period			319,736	312,114
Net income (loss)			(4,402)	32,231
Balance at end of period	315,334	344,345	315,334	344,345
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period			33,504	30,275
Foreign currency translation			(667)	(1,128)
Acquisition of the 50% noncontrolling interest in Geostream (Note 3)			(31,196)
Net income (loss)			444	(410)
Balance at end of period	2,085	28,737	2,085	28,737
Geostream
Schedule of Equity Component [Line Items]
Percentage of noncontrolling interest acquired	50.00%		50.00%		50.00%	26.00%
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Acquisition of the 50% noncontrolling interest in Geostream (Note 3)	$ 22,432	$ 0	$ 22,432	$ 0