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Segment Reporting - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Segment Reporting Information [Line Items]    
Goodwill $ 27,673us-gaap_Goodwill $ 30,398us-gaap_Goodwill
Automotive Segments    
Segment Reporting Information [Line Items]    
Goodwill 21,368us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= thrm_AutomotiveSegmentsMember
 
Industrial Segments    
Segment Reporting Information [Line Items]    
Goodwill $ 6,305us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= thrm_IndustrialSegmentsMember