The following table sets forth the changes in the carrying amount of the Company’s goodwill by segment for the years ended December 31, 2019 and 2018.

	December 31,
	2019		2018
Fluoroproducts:
Balance at January 1,	$	89	$	85
Acquisition of business		—		4
Balance at December 31,		89		89
Chemical Solutions:
Balance at January 1,		51		55
Goodwill impairment		—		(4	)
Balance at December 31,		51		51
Titanium Technologies:
Balance at January 1,		13		13
Balance at December 31,		13		13
Total goodwill	$	153	$	153

Chemours consists of three operating segments: Fluoroproducts, Chemical Solutions, and Titanium Technologies. The Company defines its reporting units as one level below these operating segments, with the exception of the Titanium Technologies segment, which is both an operating segment and a reporting unit. The Company tested the goodwill balances attributable to each of its reporting units for potential impairment on October 1, 2019 and 2018, the dates of Chemours’ annual goodwill assessment, and concluded that $4 of goodwill associated with the Performance Chemicals and Intermediates reporting unit in the Chemical Solutions segment was impaired at October 1, 2018. No further goodwill impairments were recorded for the years ended December 31, 2019 and 2018, as the fair values of the Company’s other reporting units that carry goodwill exceeded each respective reporting unit’s carrying amount on October 1, 2019 and 2018.

The total accumulated impairment losses included in the Company’s goodwill balance at December 31, 2019 and 2018 amounted to $4.

The following table sets forth the gross carrying amounts and accumulated amortization of the Company’s other intangible assets by major class at December 31, 2019 and 2018.

	December 31, 2019							December 31, 2018
	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Customer lists	$	9	$	(8	)	$	1	$	9	$	(8	)	$	1
Customer relationships		22		(8	)		14		22		(3	)		19
Patents		19		(19	)		—		19		(19	)		—
Purchased trademarks		5		(3	)		2		5		(3	)		2
Purchased and licensed technology		3		(3	)		—		3		(3	)		—
Other (1)		10		(6	)		4		10		(4	)		6
Total other intangible assets, net	$	68	$	(47	)	$	21	$	68	$	(40	)	$	28

The aggregate pre-tax amortization expense for definite-lived intangible assets was $7, $6, and $4 for the years ended December 31, 2019, 2018, and 2017, respectively. The estimated aggregate pre-tax amortization expense for 2020, 2021, 2022, 2023, and 2024 is $7, $7, $5, $1, and less than $1, respectively. Definite-lived intangible assets are amortized over their estimated useful lives, generally for periods ranging from five to 20 years. The reasonableness of the useful lives of these assets is periodically evaluated. The Company does not have any indefinite-lived intangible assets.