Pretax Amounts Recognized in Other Comprehensive (Loss) Income (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Actuarial Losses/(gains)	$ (158)	$ 78	$ 36
Establish prior service cost		509
Amortization prior service cost		(509)
Pretax amounts recognized in other comprehensive (loss) income	(158)	78	36
Gentherm GmbH
Defined Benefit Plan Disclosure [Line Items]
Actuarial Losses/(gains)	143	(229)	718
Amortization of actuarial losses	(73)	(78)	(48)
Pretax amounts recognized in other comprehensive (loss) income	$ 70	$ (307)	$ 670

Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan.

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Amount, before tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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