(3) Goodwill, Customer Relationships and Other Intangible Assets

Goodwill, customer relationships and other intangible assets consisted of the following:



	September 30, 2018		December 31, 2017
	(Dollars in millions)
Goodwill	$	11,132	10,837
Customer relationships, less accumulated amortization of $659 and $126	$	7,801	8,845
Other intangible assets subject to amortization:
Trade names, less accumulated amortization of $24 and $4	106		126
Developed technology, less accumulated amortization of $51 and $9	295		252
Total other intangible assets, net	$	401	378

Our goodwill balance at December 31, 2017 includes $16 million of goodwill that was allocated to us from CenturyLink associated with differences in the deferred state income taxes that CenturyLink expects to realize due to its consolidation of our results of operations into its state tax returns.

Total amortization expense for intangible assets for the successor three and nine months ended September 30, 2018 was $204 million and $595 million, respectively, and the predecessor three and nine months ended September 30, 2017 was $49 million and $153 million, respectively. As of the successor date of September 30, 2018, the gross carrying amount of goodwill, customer relationships, indefinite-life and other intangible assets was $20.1 billion.

We estimate that total amortization expense for intangible assets for the successor years ending December 31, 2018 through 2022 will be as follows:



	(Dollars in millions)
2018 (remaining three months)	$	202
2019	805
2020	805
2021	805
2022	794

The following table shows the rollforward of goodwill from December 31, 2017 through September 30, 2018:



	(Dollars in millions)
As of December 31, 2017	$	10,837
Purchase accounting and other adjustments	353
Effect of foreign currency rate change	(58		)
As of September 30, 2018	$	11,132