pre_text: (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.
table: As of December 31
table: 2019 2018
table: (Dollars in million)
table: Goodwill $21,534 28,031
table: Customer relationships, less accumulated amortization of $9,809 and $8,492 $7,596 8,911
table: Indefinite-life intangible assets $269 269
table: Other intangible assets subject to amortization:
table: Capitalized software, less accumulated amortization of $2,957 and $2,616 $1,599 1,468
table: Trade names, less accumulated amortization of $91 and $61 103 131
table: Total other intangible assets, net $1,971 1,868
question: Analyse this data from a financial earnings document. What is the total amortization expense for intangible assets for 2017, 2018 and 2019?