Intangible assets, net of accumulated amortization, consisted of the following (in millions):


		December 31, 2025						December 31, 2024
	Estimated Useful Lives (Years)	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Customer contracts and relationships	1 – 20	$	3,034	$	(1,295)	$	1,739	$	2,677	$	(1,015)	$	1,662

Other agreements	15 – 70	29		(14)		15		28		(13)		15
Intangible assets (1) (2)		$	3,063	$	(1,309)	$	1,754	$	2,705	$	(1,028)	$	1,677

(1)We include rights-of-way, which are intangible assets, within property and equipment. See Note 7 for a discussion of property and equipment.

(2)The increase in intangible assets in 2025 is associated with the assets acquired during the period. See Note 8 for additional information.

Intangible assets that have finite lives are tested for impairment when events or circumstances indicate that the carrying value may not be recoverable. We did not recognize any impairments of finite-lived intangible assets during the three years ended December 31, 2025.

The majority of our finite-lived intangible assets are amortized under the declining balance method. Amortization expense for finite-lived intangible assets for the years ended December 31, 2025, 2024 and 2023 was $280 million, $262 million and $291 million, respectively. We estimate that our amortization expense related to finite-lived intangible assets for the next five years will be as follows (in millions):