Summary of Significant Accounting Principles and Practices (Tables)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Schedule of Estimated Useful Lives of Assets

Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets, which are generally as follows:

Asset Description	Estimated Useful Life
Software	Lesser of the life of an associated license, or 4 to 7 years
Leasehold improvements	Lesser of estimated useful life or lease term
Furniture, fixtures and equipment	4 to 10 years
Computer equipment	4 to 6 years
Buildings	35 years
Vehicles	5 to 6 years

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
Customer-related and contract-based	In line with underlying cash flows	7 to 23 years
Tradenames	Straight-line	1 to 10.5 years
Technology and other intangibles	Straight-line	5 to 7 years

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

	2025						2024
As of December 31	Gross Carrying Amount		Accumulated Amortization and Impairment		Net Carrying Amount (1)		Gross Carrying Amount		Accumulated Amortization and Impairment		Net Carrying Amount
Customer-related and contract-based	$	7,738	$	2,644	$	5,094	$	7,994	$	2,050	$	5,944
Tradenames	716		121		595		812		66		746
Technology and other	369		331		38		366		313		53
Total	$	8,823	$	3,096	$	5,727	$	9,172	$	2,429	$	6,743

(1)Aon disposed of $760 million of net intangible assets that related to the NFP Wealth business.