Intangible Assets

12 Months Ended

Dec. 31, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Intangible Assets

8. Intangible Assets

Intangible assets consist of the following:

	(Stated in millions)
	2020						2019
	Gross		Accumulated		Net Book		Gross		Accumulated		Net Book
	Book Value		Amortization		Value		Book Value		Amortization		Value
Customer Relationships	$	1,744	$	485	$	1,259	$	3,779	$	868	$	2,911
Technology/Technical Know-How		1,284		488		796		2,498		779		1,719
Tradenames		767		166		601		1,885		264		1,621
Other		1,488		689		799		1,514		676		838
	$	5,283	$	1,828	$	3,455	$	9,676	$	2,587	$	7,089

Customer relationships are generally amortized over periods ranging from 18 to 28 years, technology/technical know-how are generally amortized over periods ranging from 10 to 18 years, and tradenames are generally amortized over periods ranging from 15 to 30 years.

Amortization expense was $371 million in 2020, $618 million in 2019 and $673 million in 2018.

Based on the carrying value of intangible assets at December 31, 2020, amortization expense for the subsequent five years is estimated to be as follows: 2021: $307 million, 2022: $304 million, 2023: $293 million, 2024: $269 million and 2025: $259 million.