Identifiable intangible assets consist of acquired customer contracts and relationships, trademarks and non-compete agreements. Amortization expense related to intangible assets was $55.8, $56.3 and $104.9 for the years ended September 30, 2020, September 30, 2019 and September 30, 2018, respectively. These assets are amortized over their estimated useful lives of which the reasonableness is continually evaluated by the Company.

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

		September 30, 2020					September 30, 2019
	Useful Life	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Customer relationships	6-21 yrs.	$	666.3	$	(448.3	)	$	639.6	$	(393.3	)
Trademarks	4-12 yrs.		3.8		(2.0	)		4.8		(1.7	)
Non-compete agreements	5 yrs.		2.7		(1.2	)		2.7		(0.6	)
Total intangible assets		$	672.8	$	(451.5	)	$	647.1	$	(395.6	)

The weighted average amortization period for intangible assets is 17.5 years. Amortization expense is anticipated to be as follows in future years:

Fiscal Year Ended September 30,
2021	$	46.9
2022		40.5
2023		33.6
2024		26.8
2025		22.1
2026 and thereafter		51.4
	$	221.3

The following is a summary of the goodwill activity for the periods ended September 30, 2019 and September 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		64.4		—			64.4
Impairment Loss		—		(15.5	)		(15.5	)
Balance, September 30, 2020	$	1,680.4	$	178.9		$	1,859.3

The Company performed its annual goodwill impairment assessment as of July 1, 2020 utilizing a quantitative test approach as described in Note 2 “Summary of Significant Accounting Policies”. During the analysis it was identified that the BrightView Tree Company reporting unit’s carrying value exceeded its fair value, thus indicating an impairment. As a result of the analysis and in conjunction with the initiation and conclusion of the sale of the BrightView Tree Company reporting unit in the fourth quarter of fiscal 2020, an impairment loss of $15.5 was recognized within the Tree reporting unit which is reported within the Development Services operating segment. The goodwill impairment loss was recognized during the fourth quarter of fiscal 2020 and is included in Selling, general and administrative expense in the Consolidated Statements of Operations for the fiscal year ended September 30, 2020.

During the year ended September 30, 2020, the Company acquired, through a series of separate transactions, 100% of the operations of six unrelated Maintenance Services companies. The Company paid approximately $90.3 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, including customer relationships and non-compete agreements of $26.7. 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.

During the year ended September 30, 2019, the Company acquired, through a series of separate transactions, 100% of the operations of six unrelated Maintenance Services companies. The Company paid approximately $64.0 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, including customer relationships and non-compete agreements of $17.2. 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.

On September 30, 2020, the Company completed the sale of two of its fully owned subsidiaries in separate transactions. Total consideration received in the transactions was $32.3, which consisted of $29.3 in cash and, included in one of the transactions, a promissory note of $3.0. The combined pre-tax loss on sale of the transactions totaling $5.7 is included in Selling, general and administrative expense in the Consolidated Statements of Operations for the fiscal year ended September 30, 2020. Each of the Maintenance Services and Development Services operating segments include the operations of one of the divested entities, and their results of operations through the closing date are included in the Consolidated Statements of Operations for the fiscal years ended September 30, 2020, September 30, 2019, and September 30, 2018.