Note 12—Goodwill and Other Intangible Assets

The changes in the carrying amount of goodwill by segment were as follows:


	Interconnect		Cable
	Products and		Products and
	Assemblies		Solutions		Total
Goodwill at December 31, 2018	$	3,956.7	$	146.5	$	4,103.2
Acquisition-related		347.1		—		347.1
Foreign currency translation		(10.4)		—		(10.4)
Goodwill at March 31, 2019	$	4,293.4	$	146.5	$	4,439.9

The increase in goodwill, net of foreign currency translation, during the first three months of 2019 is primarily due to the acquisition of SSI in January 2019, which is included in the Interconnect Products and Assemblies segment.

Other than goodwill noted above, the Company’s intangible assets as of March 31, 2019 and December 31, 2018 were as follows:


		March 31, 2019						December 31, 2018
	Weighted	Gross				Net		Gross				Net
	Average	Carrying		Accumulated		Carrying		Carrying		Accumulated		Carrying
	Life (years)	Amount		Amortization		Amount		Amount		Amortization		Amount
Customer relationships	10	$	413.8	$	243.9	$	169.9	$	399.2	$	234.7	$	164.5
Proprietary technology	11		140.9		63.6		77.3		107.5		60.5		47.0
Backlog and other	2		46.5		46.2		0.3		34.0		33.7		0.3
Total intangible assets (definite-lived)	9		601.2		353.7		247.5		540.7		328.9		211.8

Trade names (indefinite-lived)			186.1		—		186.1		186.1		—		186.1
		$	787.3	$	353.7	$	433.6	$	726.8	$	328.9	$	397.9

Intangible assets are included in Intangibles, net and other long-term assets in the accompanying Condensed Consolidated Balance Sheets. The increase in the carrying amounts of intangible assets during the first quarter of 2019 was primarily due to intangible assets acquired as a result of the SSI acquisition. The amortization expense for the three months ended March 31, 2019 and 2018 was approximately $24.8 and $11.9, respectively. The amortization expense during the first three months of 2019 includes $12.5 related to the amortization of acquired backlog. As of March 31, 2019, amortization expense relating to the Company’s current intangible assets estimated for the remainder of 2019 is approximately $35.1 and for each of the next five fiscal years is approximately $41.8 in 2020, $37.1 in 2021, $29.7 in 2022, $27.0 in 2023 and $23.9 in 2024.