Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes in the Net Carrying Amount of Goodwill by Operating Segment

The changes in the net carrying amount of goodwill for the years ended December 31, 2020 and 2019, respectively, are as follows (in millions):

Balance as of January 1, 2019	$	8,171
Goodwill related to current year acquisitions	34
Goodwill related to disposals	(11)
Goodwill related to prior year acquisitions	2
Foreign currency translation	(31)
Balance as of December 31, 2019	$	8,165
Goodwill related to current year acquisitions	314
Goodwill related to disposals	(3)
Foreign currency translation	190
Balance as of December 31, 2020	$	8,666

Schedule of Other Intangible Assets by Asset Class

Amortization basis and estimated useful lives by intangible asset type are generally as follows:

Intangible Asset Description	Amortization Basis	Estimated Useful Life
Tradenames	Straight-line	1 to 3 years
Customer-related and contract-based	In line with underlying cash flows	7 to 20 years
Technology and other	Straight-line	5 to 7 years

Other intangible assets by asset class are as follows (in millions):

	As of December 31
	2020						2019
	Gross Carrying Amount		Accumulated Amortization and Impairment		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization and Impairment		Net Carrying Amount
Customer-related and contract-based	$	2,337	$	1,775	$	562	$	2,264	$	1,600	$	664
Tradenames (1)	14		13		1		1,029		956		73
Technology and other	435		358		77		380		334		46
Total	$	2,786	$	2,146	$	640	$	3,673	$	2,890	$	783

(1)In 2020, Aon wrote off $1.0 billion of fully amortized tradenames, including the Hewitt and Benfield tradenames. The company no longer expects to receive economic benefits from these tradenames.

Schedule of Estimated Future Amortization Expense on Intangible Assets

The estimated future amortization for finite-lived intangible assets as of December 31, 2020 is as follows (in millions):

	Estimated Future Amortization
For the years ended
2021	$	144
2022	102
2023	91
2024	73
2025	59
Thereafter	171
Total	$	640