Note 5 - Goodwill and Acquired Intangible Assets
Intangible assets, other than goodwill, consisted of the following as of December 31, 2025 and 2024, respectively:
(in millions)Gross Carrying AmountAccumulated AmortizationNetWeighted Average Amortization Period in Years
Intangible assets subject to amortization:
Customer relationships$288.1 $(153.4)$134.7 14.6
Acquired technology331.3 (284.2)47.1 6.2
Brand portfolio11.5 (9.0)2.5 7.8
Total intangible assets subject to amortization$630.9 $(446.6)$184.3 
Intangible assets not subject to amortization:
Pre-Acquisition ZI brand portfolio$33.0 $— $33.0 
Total intangible assets not subject to amortization
$33.0 $— $33.0 
Total intangible assets$663.9 $(446.6)$217.3 
(in millions)Gross Carrying AmountAccumulated AmortizationNetWeighted Average Amortization Period in Years
Intangible assets subject to amortization:
Customer relationships$288.1 $(133.2)$154.9 14.5
Acquired technology331.3 (246.6)84.7 6.3
Brand portfolio11.5 (8.3)3.2 7.8
Total intangible assets subject to amortization$630.9 $(388.1)$242.8 
Intangible assets not subject to amortization:
Pre-Acquisition ZI brand portfolio$33.0 $— $33.0 
Total intangible assets not subject to amortization$33.0 $— $33.0 
Total intangible assets$663.9 $(388.1)$275.8 
Amortization expense was $58.5 million, $59.8 million, and $61.0 million for the years ended December 31, 2025, 2024, and 2023, respectively.
Future amortization expense for intangible assets as of December 31, 2025 is as follows:
(in millions)Estimated Amortization Expense
For years ended December 31,
2026$48.6 
202738.3 
202821.9 
202918.0 
203015.8 
Thereafter41.7 
Total amortization expense$184.3 
Goodwill was $1,692.7 million as of December 31, 2025, 2024 and 2023. There were no changes to the carrying amount of goodwill during the years presented. Based on the results of the Company’s impairment assessment, the Company did not recognize any impairment of goodwill during the years ended December 31, 2025, 2024, and 2023.

About Goodwill & Intangibles Disclosures

Goodwill and intangible asset disclosures reveal the premium paid in acquisitions and how management assesses whether that premium retains its value. Since goodwill is no longer amortized under US GAAP, the annual impairment test is the only mechanism that adjusts carrying values downward — making the assumptions behind that test critically important for investors.

Key signals: a history of goodwill impairments suggests management consistently overpays for acquisitions. Watch the gap between reporting unit fair value and carrying amount — when fair value exceeds carrying amount by less than 10-20%, a small decline in business performance could trigger a write-down. For finite-lived intangibles, examine useful life assumptions across customer relationships, technology, and trade names; aggressive estimates inflate near-term earnings. Compare total intangibles-to-total-assets ratios against peers to assess acquisition dependency. Rising goodwill as a percentage of equity can signal balance sheet fragility.