Table:
|  | As of December 31 |  |
| --- | --- | --- |
|  | 2019 | 2018 |
|  | (Dollars in million) |  |
| Goodwill | $21,534 | 28,031 |
| Customer relationships, less accumulated amortization of $9,809 and $8,492 | $7,596 | 8,911 |
| Indefinite-life intangible assets | $269 | 269 |
| Other intangible assets subject to amortization: |  |  |
| Capitalized software, less accumulated amortization of $2,957 and $2,616 | $1,599 | 1,468 |
| Trade names, less accumulated amortization of $91 and $61 | 103 | 131 |
| Total other intangible assets, net | $1,971 | 1,868 |
Paragraphs:
(4) Goodwill, Customer Relationships and Other Intangible Assets
Goodwill, customer relationships and other intangible assets consisted of the following:
Our goodwill was derived from numerous acquisitions where the purchase price exceeded the fair value of the net assets acquired (including the acquisition described in Note 2—Acquisition of Level 3). As of December 31, 2019, the weighted average remaining useful lives of the intangible assets were approximately 8 years in total, approximately 9 years for customer relationships, 4 years for capitalized software and 3 years for trade names.
Total amortization expense for intangible assets for the years ended December 31, 2019, 2018 and 2017 was $1.7 billion, $1.8 billion and $1.2 billion, respectively. As of December 31, 2019, the gross carrying amount of goodwill, customer relationships, indefinite-life and other intangible assets was $44.0 billion.
Question:
How was goodwill derived?
Answer: from numerous acquisitions where the purchase price exceeded the fair value of the net assets acquired (including the acquisition described in Note 2—Acquisition of Level 3)