Related party transactions (Details)	6 Months Ended
Jun. 30, 2016 company
Related Party Transactions [Abstract]
Number of affiliated companies	2

Related Party Transaction, Number of Affiliated Companies

No definition available.

Name:	tgen_RelatedPartyTransactionNumberOfAffiliatedCompanies
Namespace Prefix:	tgen_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration