The carrying amount of goodwill attributable to each reportable segment with goodwill balances and the changes in those balances during the six month period ended March 31, 2020 are as follows:

	Reinforcement Materials			Performance Chemicals			Total
	(In millions)
Balance at September 30, 2019	$	50		$	40		$	90
Foreign currency impact		(6	)		(2	)	$	(8	)
Balance at March 31, 2020	$	44		$	38		$	82

The following table provides information regarding the Company’s intangible assets:

	March 31, 2020							September 30, 2019
	Gross Carrying Value		Accumulated Amortization			Net Intangible Assets		Gross Carrying Value		Accumulated Amortization			Net Intangible Assets
	(In millions)
Intangible assets with finite lives
Developed technologies	$	49	$	(5	)	$	44	$	50	$	(5	)	$	45
Trademarks		8		(1	)		7		8		—			8
Customer relationships		48		(12	)		36		57		(14	)		43
Total intangible assets⁽¹⁾	$	105	$	(18	)	$	87	$	115	$	(19	)	$	96

⁽¹⁾The decrease in value of Total intangible assets as of March 31, 2020 was primarily driven by the impact of foreign currency translation, which had a total impact of $7 million.

Intangible assets are amortized over their estimated useful lives, which range between twelve and twenty-five years, with a weighted average amortization period of approximately nineteen years. Amortization expense for both the three months ended March 31, 2020 and 2019 was $2 million and is included in Cost of sales, Selling and administrative expenses, and Research and technical expenses in the Consolidated Statements of Operations. Amortization expense for both the six months ended March 31, 2020 and 2019 was $3 million and is included in Cost of sales, Selling and administrative expenses, and Research and technical expenses in the Consolidated Statements of Operations. Total amortization expense is estimated to be approximately $6 million each year for the next five fiscal years.