Pension and Other Post Retirement Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Payment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Vesting period	6 years
Discount rate for net periodic service cost	3.40%	3.25%	4.25%
Discount rate for benefit obligation	3.25%	3.40%	3.25%
Insurance policy value		$ 2,112,000	$ 1,993,000
Tax (expense) benefit recognized in other comprehensive income	$ 14,000	(23,000)	121,000
Pretax unrecognized actuarial losses recorded in accumulated other comprehensive income (loss)	302,000	266,000
Expected pretax unrecognized actuarial losses recorded in accumulated other comprehensive income (loss ) in next fiscal year	0
Contributions to 401(k) plan	$ 1,289,000	$ 959,000	543,000
Gentherm GmbH
Defined Benefit Plan Disclosure [Line Items]
Discount rate for benefit obligation	1.69%	2.21%
Tax (expense) benefit recognized in other comprehensive income	$ 171,000	$ (211,000)	$ 559,000
Pretax unrecognized actuarial losses recorded in accumulated other comprehensive income (loss)	2,406,000	1,821,000
Expected pretax unrecognized actuarial losses recorded in accumulated other comprehensive income (loss ) in next fiscal year	73,000
Pension benefit obligation	4,000,000
Underfunded defined benefit plan	4,000,000	$ 3,647,000
Defined benefit plan, expected employer contribution in next fiscal year	0
Chief Executive Officer
Defined Benefit Plan Disclosure [Line Items]
Annual retirement payment	$ 300,000,000
Number of expected annual retirement benefit payments | Payment	15
Annual retirement benefit payments, earliest date	Jan. 01, 2018