Components of Net Periodic Pension Benefit Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 101	$ 387
Interest cost	$ 114	111	98
Amortization of prior service cost	(342)	509
Net periodic benefit cost	114	721	485
Gentherm GmbH
Defined Benefit Plan Disclosure [Line Items]
Interest cost	147	130	154
Return on plan assets	(130)	(121)	(125)
Net periodic benefit cost	90	87	77
Amortization of actuarial loss (gains)	$ 73	$ 78	$ 48