Identifiable intangible assets consist of acquired customer contracts and relationships, trademarks and non-compete agreements. Amortization expense related to intangible assets was $13.6 and $13.9 for the three months ended June 30, 2020 and 2019, respectively. Amortization expense related to intangible assets was $40.6 and $42.9 for the nine months ended June 30, 2020 and 2019, respectively. These assets are amortized over their estimated useful lives of which the reasonableness is continually evaluated by the Company.

Intangible assets as of June 30, 2020 and September 30, 2019 consisted of the following:

		June 30, 2020					September 30, 2019
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Customer relationships	6-21 yrs.	$	656.9	$	(433.4	)	$	639.6	$	(393.3	)
Trademarks	4-12 yrs.		4.8		(1.9	)		4.8		(1.7	)
Non-compete agreements	5 yrs.		2.7		(1.0	)		2.7		(0.6	)
Total intangible assets		$	664.4	$	(436.3	)	$	647.1	$	(395.6	)

The following is a summary of the goodwill activity for the periods ended September 30, 2019 and June 30, 2020:

	Maintenance Services		Development Services		Total
Balance, September 30, 2018	$	1,572.4	$	194.4	$	1,766.8
Acquisitions		43.6		—		43.6
Balance, September 30, 2019		1,616.0		194.4		1,810.4
Acquisitions		67.1		—		67.1
Balance, June 30, 2020	$	1,683.1	$	194.4	$	1,877.5

During the nine months ended June 30, 2020, the Company acquired, through a series of separate transactions, 100% of the operations of five unrelated Maintenance Services companies. The Company paid approximately $86.5 in 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 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 valuation process to determine fair values is not yet complete. The Company will finalize the amounts recognized as it obtains the information necessary to complete the analysis, but no later than one year from the acquisition date. The identifiable assets acquired were primarily intangible assets, principally customer relationships of $17.3. The amount allocated to goodwill is reflective of the benefits the Company expects to realize from anticipated synergies and the acquired assembled workforce. The Company expects a portion of the goodwill resulting from these acquisitions will be deductible for tax purposes.