Identifiable intangible assets consist of acquired customer contracts and relationships, trademarks, and non-compete agreements. Amortization expense related to intangible assets was $8.6 and $10.8 for the three months ended June 30, 2024 and 2023, respectively. Amortization expense related to intangible assets was $27.4 and $33.7 for the nine months ended June 30, 2024 and 2023, respectively. These assets are amortized over their estimated useful lives of which the reasonableness is continually evaluated by the Company. The weighted average amortization periods of intangible assets acquired during the nine months ended June 30, 2023 was seven years.

Intangible assets, net, as of June 30, 2024 and September 30, 2023 consisted of the following:


		June 30, 2024					September 30, 2023
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Customer relationships	6-21 yrs.	$	715.9	$	(611.8	)	$	725.5	$	(594.1	)
Trademarks	12 yrs.		—		—			3.8		(2.9	)
Non-compete agreements	5 yrs.		—		—			2.7		(2.7	)
Total intangible assets		$	715.9	$	(611.8	)	$	732.0	$	(599.7	)

The following is a summary of the goodwill activity for the periods ended September 30, 2023 and June 30, 2024:


	Maintenance Services			Development Services		Total
Balance, September 30, 2022	$	1,792.7		$	216.1	$	2,008.8
Acquisitions (1)		10.7			1.9		12.6
Balance, September 30, 2023	$	1,803.4		$	218.0	$	2,021.4
Acquisitions (1)		0.1			—		0.1
Divestiture		(5.8	)		—		(5.8	)
Balance, June 30, 2024	$	1,797.7		$	218.0	$	2,015.7

(1)

The acquisitions adjustment includes the immaterial impact of foreign currency adjustments during the period.

During the nine months ended June 30, 2023, the Company acquired, through a series of separate transactions, 100% of the operations of three unrelated companies, all of which were allocated to Maintenance Services. The Company paid approximately $13.8 in aggregate consideration for the acquisitions, net of cash acquired. The Company accounted for the business combinations under the acquisition method and, accordingly, recorded the assets acquired and liabilities assumed at their estimated fair market values based on management’s preliminary estimates, with the excess allocated to goodwill. The purchase accounting related to these acquisitions was finalized within one year from each acquisition date. As a result of the final purchase accounting, certain of the fair value amounts previously estimated were adjusted during the measurement period. The fair values were primarily estimated using Level 3 assumptions within the fair value hierarchy, including estimated future cash flows, discount rates and other factors. The measurement period adjustments were not material to the Consolidated Balance Sheets as of June 30, 2024 and September 30, 2023. The identifiable assets acquired were primarily customer relationship intangible assets of $4.0. The amount allocated to goodwill is reflective of the benefits the Company expects to realize from anticipated synergies and the acquired assembled workforce. A portion of the goodwill resulting from these acquisitions is deductible for tax purposes.