Series C Convertible Preferred Stock Installments (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Class Of Stock [Line Items]
Dividend, installment payments	$ 665
Principal, installment payments	8,280
Total, installment payments	$ 8,945

Net of dividend and principal installment payments.

No definition available.

Name:	thrm_NetOfDividendAndPrincipalInstallmentPayments
Namespace Prefix:	thrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration