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NET (LOSS) INCOME PER COMMON SHARE (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended	12 Months Ended	0 Months Ended	3 Months Ended						6 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2014	Jul. 09, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jul. 09, 2014	Dec. 31, 2013	Dec. 31, 2012
Anti-dilutive shares (in shares)				1,110,600
Common shares outstanding, basic:
Weighted average common shares outstanding - Basic	60,415,981	60,299,766	60,360,515
Common shares outstanding, diluted:
Weighted average common shares outstanding - Basic	60,415,981	60,299,766	60,360,515
Weighted-average common shares outstanding, diluted (in shares)	60,415,981	60,299,766	60,360,515
Reconciliation of the net loss attributable to GS&T and the net loss attributable to GS&T for diluted net loss per share
Net loss (income) attributable to GS&T	$ (164,003)	$ (18,290)	$ (182,294)
Net loss (income) attributable to GS&T for the computation of diluted net loss (income) per share			(182,294)
Predecessor
Anti-dilutive shares (in shares)												0
Common shares outstanding, basic:
Weighted average common shares outstanding - Basic					43,568,942	43,568,942	43,568,942	43,403,894	43,231,510	43,196,895	43,161,510	43,568,942	43,249,070	41,727,075
Common shares outstanding, diluted:
Weighted average common shares outstanding - Basic					43,568,942	43,568,942	43,568,942	43,403,894	43,231,510	43,196,895	43,161,510	43,568,942	43,249,070	41,727,075
Weighted-average common shares outstanding, diluted (in shares)					43,568,942	43,568,942	43,568,942	43,403,894	43,231,510	43,196,895	43,161,510	43,568,942	43,249,070	41,727,075
Reconciliation of the net loss attributable to GS&T and the net loss attributable to GS&T for diluted net loss per share
Net loss (income) attributable to GS&T					892,919	(60,524)	(39,105)	(19,175)	(35,034)	(45,369)	(48,163)	793,291	(147,741)	(144,928)
Net loss (income) attributable to GS&T for the computation of diluted net loss (income) per share												$ 793,291	$ (147,741)	$ (144,928)