Goodwill and Acquired Intangibles

12 Months Ended

Dec. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying amount of goodwill by segment were as follows (in millions):


	Aeronautics		MFC		RMS		Space		Total
Balance at December 31, 2018	$	171	$	2,262	$	6,751	$	1,585	$	10,769

Distributed Energy Solutions divestiture	—		(175)		—		—		(175)
Other	—		2		7		1		10
Balance at December 31, 2019	171		2,089		6,758		1,586		10,604
Acquisitions	16		—		—		173		189
Other	—		2		10		1		13
Balance at December 31, 2020	$	187	$	2,091	$	6,768	$	1,760	$	10,806

The gross carrying amounts and accumulated amortization of our acquired intangible assets consisted of the following (in millions):


	2020						2019
	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Finite-Lived:
Customer programs	$	3,184	$	(1,199)	$	1,985	$	3,184	$	(967)	$	2,217
Customer relationships	366		(287)		79		344		(243)		101
Other	85		(24)		61		53		(45)		8
Total finite-lived intangibles	3,635		(1,510)		2,125		3,581		(1,255)		2,326
Indefinite-Lived:
Trademark	887		—		887		887		—		887
Total acquired intangibles	$	4,522	$	(1,510)	$	3,012	$	4,468	$	(1,255)	$	3,213

Acquired finite-lived intangible assets are amortized to expense primarily on a straight-line basis over the following estimated useful lives: customer programs, from nine to 20 years; customer relationships, from four to 10 years; and other intangibles, from three to 10 years.

Amortization expense for acquired finite-lived intangible assets was $271 million, $284 million and $296 million in 2020, 2019 and 2018. Estimated future amortization expense is as follows: $290 million in 2021; $252 million in 2022; $249 million in 2023; $245 million in 2024; $223 million in 2025 and $866 million thereafter.