ORGANIZATION AND BASIS OF PRESENTATION (Details)	Mar. 31, 2014 foreign_country	May 05, 2014 Subsequent Event Forest Shareholders	May 05, 2014 Subsequent Event Sabine Shareholders
Subsequent Event
Percentage of stock held upon completion of merger (as a percent)		26.50%	73.50%
Exploratory and development interests in foreign countries	2

Represents the number of foreign countries in which the entity has exploratory and development interests.

No definition available.

Name:	fst_ExploratoryAndDevelopmentInterestsInForeignCountriesNumber
Namespace Prefix:	fst_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant