Segment Information About Reported Segment Product Revenues by Product Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Product revenues	$ 240,056	$ 261,504	$ 741,303	$ 792,490
Automotive Segments
Segment Reporting Information [Line Items]
Product revenues	228,243	238,849	700,300	724,420
Automotive Segments | Climate Control Seat (CCS)
Segment Reporting Information [Line Items]
Product revenues	88,133	97,578	270,924	276,191
Automotive Segments | Seat Heaters
Segment Reporting Information [Line Items]
Product revenues	71,030	70,768	218,578	235,164
Automotive Segments | Steering Wheel Heaters
Segment Reporting Information [Line Items]
Product revenues	16,621	18,095	49,620	53,192
Automotive Segments | Automotive Cables
Segment Reporting Information [Line Items]
Product revenues	20,361	24,961	66,316	77,471
Automotive Segments | Battery Thermal Management (BTM)
Segment Reporting Information [Line Items]
Product revenues	11,890	7,461	31,531	18,863
Automotive Segments | Electronics
Segment Reporting Information [Line Items]
Product revenues	11,729	12,590	36,035	44,409
Automotive Segments | Other Automotive
Segment Reporting Information [Line Items]
Product revenues	8,479	7,396	27,296	19,130
Industrial Segments
Segment Reporting Information [Line Items]
Product revenues	11,813	22,655	41,003	68,070
Industrial Segments | Remote Power Generation
Segment Reporting Information [Line Items]
Product revenues	3,477	4,378	11,181	14,310
Industrial Segments | Industrial Chambers
Segment Reporting Information [Line Items]
Product revenues		9,829	3,418	30,460
Industrial Segments | Gentherm Medical
Segment Reporting Information [Line Items]
Product revenues	$ 8,336	$ 8,448	$ 26,404	$ 23,300