GOODWILL AND INTANGIBLE ASSETS

The following table summarizes changes to goodwill by reportable segment:



	U.S. Water Services
Millions
Balance as of December 31, 2016		$131.2
Acquired Goodwill (a)	16.9
Other Adjustments (b)	0.2
Balance as of December 31, 2017	148.3
Other Adjustments (b)	0.2
Balance as of December 31, 2018		$148.5


(a)	See Note 6. Acquisitions.


(b)	Finalization of purchase price accounting for U.S. Water Services’ acquisition of WEST was completed in 2017 and acquisition of Tonka Water was completed in 2018 resulting in adjustments in those periods to the goodwill recorded at the time of acquisition.

NOTE 7. GOODWILL AND INTANGIBLE ASSETS (Continued)

The following table summarizes changes to intangible assets, net, for the year ended December 31, 2018:



	December 31, 2017		Additions		Amortization	December 31, 2018
Millions
Intangible Assets
Definite-Lived Intangible Assets
Customer Relationships		$54.7		$0.2	$(4.2)		$50.7
Developed Technology and Other (a)	6.3		2.6		(1.4)	7.5
Total Definite-Lived Intangible Assets	61.0		2.8		(5.6)	58.2
Indefinite-Lived Intangible Assets
Trademarks and Trade Names	16.6		—		n/a	16.6
Total Intangible Assets		$77.6		$2.8	$(5.6)		$74.8


(a)	Developed Technology and Other includes patents, non-compete agreements, land easements and trade names with finite lives.

Customer relationships have a remaining useful life of approximately 19 years, and developed technology and other have remaining useful lives ranging from approximately 4 years to approximately 10 years (weighted average of approximately 6 years). The weighted average remaining useful life of all definite-lived intangible assets as of December 31, 2018, is approximately 17 years.

Amortization expense of intangible assets for the year ended December 31, 2018, was $5.6 million ($5.5 million in 2017; $5.2 million in 2016). Accumulated amortization was $20.4 million and $14.8 million as of December 31, 2018, and December 31, 2017, respectively. Estimated amortization expense for definite-lived intangible assets is $5.3 million in 2019, $4.9 million in 2020, $4.9 million in 2021, $4.6 million in 2022, $4.3 million in 2023 and $34.2 million thereafter.