NET (LOSS) INCOME PER SHARE (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
NET (LOSS) INCOME PER SHARE [Abstract]                      
Anti-dilutive shares (in shares)                 880,465    
Common shares outstanding, basic [Abstract]                      
Weighted-average common shares outstanding, basic (in shares) 43,403,894 43,231,510 43,196,895 43,161,510 43,026,657 42,885,810 42,878,228 38,090,590 43,249,070 41,727,075 35,179,244
Common shares outstanding, diluted [Abstract]                      
Weighted-average common shares outstanding, basic (in shares) 43,403,894 43,231,510 43,196,895 43,161,510 43,026,657 42,885,810 42,878,228 38,090,590 43,249,070 41,727,075 35,179,244
Dilutive effect of convertible notes (in shares)                 0 0 0
Dilutive effect of restricted stock awards (in shares)                 0 0 78,961
Weighted-average common shares outstanding, diluted (in shares) 43,403,894 43,231,510 43,196,895 43,161,510 43,026,657 42,885,810 42,878,228 38,090,590 43,249,070 41,727,075 35,258,205
Reconciliation of net (loss) attributable to GS&T and net (loss) income attributable to GS&T for diluted net (loss) income per share [Abstract]                      
Net (loss) income attributable to GS&T $ (19,175) $ (35,034) $ (45,369) $ (48,163) $ (45,667) $ (38,449) $ (27,741) $ (33,071) $ (147,741) $ (144,928) $ 25,386
Interest expense related to convertible notes, if dilutive                 0 0 0
Net (loss) income attributable to GS&T for the computation of diluted net (loss) income per share                 $ (147,741) $ (144,928) $ 25,386