Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Summary Of Other Intangible Assets [Line Items]
Gross carrying amount	$ 231,922	$ 212,621
Accumulated amortization	158,985	129,071
Net carrying amount	72,937	83,550
Developed Technology [Member]
Summary Of Other Intangible Assets [Line Items]
Gross carrying amount	159,815	142,368
Accumulated amortization	112,494	90,729
Net carrying amount	$ 47,321	$ 51,639
Developed Technology [Member] \| Minimum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	4 years	4 years
Developed Technology [Member] \| Maximum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	6 years	6 years
Customer Relationships [Member]
Summary Of Other Intangible Assets [Line Items]
Gross carrying amount	$ 60,556	$ 58,316
Accumulated amortization	44,524	37,779
Net carrying amount	$ 16,032	$ 20,537
Customer Relationships [Member] \| Minimum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	4 years	7 years
Customer Relationships [Member] \| Maximum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	10 years	10 years
Trade names and other intangibles [Member]
Summary Of Other Intangible Assets [Line Items]
Gross carrying amount	$ 11,551	$ 11,937
Accumulated amortization	1,967	563
Net carrying amount	$ 9,584	$ 11,374
Trade names and other intangibles [Member] \| Minimum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	3 years	4 years
Trade names and other intangibles [Member] \| Maximum [Member]
Summary Of Other Intangible Assets [Line Items]
Weighted-average useful life of acquired finite-lived intangible assets	10 years	10 years

Altair Engineering Inc. 10-K