Series C Convertible Preferred Stock Installments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013
Class of Stock [Line Items]
Dividend, installment payments	$ 488
Principal, installment payments	7,780
Total, installment payments	$ 8,268

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