A summary of the activity and balances in goodwill accounts by reporting segment follows:


	Balance as of December 31, 2023		Acquisitions		Divestitures		Adjustments and Other		Balance as of December 31, 2024
Group 1	$	7,312	$	161	$	—	$	19	$	7,492
Group 2	6,445		—		—		(7)		6,438
Group 3	2,077		15		—		(40)		2,052
Total	$	15,834	$	176	$	—	$	(28)	$	15,982


	Balance as of December 31, 2022		Acquisitions		Divestitures		Adjustments and Other		Balance as of December 31, 2023
Group 1	$	6,638	$	675	$	—	$	(1)	$	7,312
Group 2	6,238		208		(2)		1		6,445
Group 3	1,575		275		—		227		2,077
Total	$	14,451	$	1,158	$	(2)	$	227	$	15,834

Adjustments to acquisitions during the year ended December 31, 2024 primarily related to changes in our valuation of property, plant and equipment and customer list intangible assets acquired as a result of obtaining new information regarding the acquisitions that closed in 2023. Adjustments to acquisitions during the year ended December 31, 2023 primarily related to changes in our valuation of tangible assets acquired and certain environmental liabilities assumed in connection with our acquisition of US Ecology.

Other intangible assets, net, includes values assigned to customer relationships, non-compete agreements and trade names, and are amortized over periods ranging from 1 to 15 years. A summary of the activity and balances by intangible asset type follows:


	Gross Intangible Assets								Accumulated Amortization								Other Intangible Assets, Net as of December 31, 2024
	Balance as of December 31, 2023		Acquisitions		Adjustments and Other		Balance as of December 31, 2024		Balance as of December 31, 2023		Additions Charged to Expense		Adjustments and Other		Balance as of December 31, 2024
Customer relationships	$	632	$	38	$	20	$	690	$	(166)	$	(69)	$	20	$	(215)	$	475

Other intangible assets	53		6		32		91		(23)		(10)		13		(20)		71
Total	$	685	$	44	$	52	$	781	$	(189)	$	(79)	$	33	$	(235)	$	546


	Gross Intangible Assets								Accumulated Amortization								Other Intangible Assets, Net as of December 31, 2023
	Balance as of December 31, 2022		Acquisitions		Adjustments and Other		Balance as of December 31, 2023		Balance as of December 31, 2022		Additions Charged to Expense		Adjustments and Other		Balance as of December 31, 2023
Customer relationships	$	1,013	$	197	$	(578)	$	632	$	(709)	$	(54)	$	597	$	(166)	$	466

Other intangible assets	145		7		(99)		53		(102)		(12)		91		(23)		30
Total	$	1,158	$	204	$	(677)	$	685	$	(811)	$	(66)	$	688	$	(189)	$	496

Based on the amortizable intangible assets recorded in the consolidated balance sheet as of December 31, 2024, amortization expense for each of the next five years is estimated as follows:


2025	$	78
2026	$	74
2027	$	67
2028	$	64
2029	$	58