Actuarial Assumptions Used to Determine Benefit Obligation and Net Periodic Service Cost (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.25%	3.40%	3.25%
Gentherm GmbH
Defined Benefit Plan Disclosure [Line Items]
Discount rate	1.69%	2.21%
Expected long term rate of return on plan assets	3.40%	3.70%