Executive Nonqualified Defined Benefit Plan - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Vesting period	6 years
Discount rate for benefit obligation and net periodic service cost	3.25%	4.25%	3.25%
Insurance policy value	$ 2,056	$ 1,962
Contributions to 401(k) plan	543	191	161
Gentherm GmbH
Defined Benefit Plan Disclosure [Line Items]
Underfunded defined benefit plan	4,505	3,679
Chief Executive Officer
Defined Benefit Plan Disclosure [Line Items]
Annual retirement payment	$ 300,000
Number of expected annual retirement benefit payments	15
Annual retirement benefit payments, earliest date	Jan. 01, 2018