Cover - USD ($)	12 Months Ended
	Dec. 31, 2023	Apr. 12, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-7933
Entity Registrant Name	Aon plc
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1539969
Entity Address, Address Line One	Metropolitan Building, James Joyce Street
Entity Address, City or Town	Dublin 1
Entity Address, Country	IE
Entity Address, Postal Zip Code	D01 K0Y8
Country Region	353
City Area Code	1
Local Phone Number	266 6000
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 70,135,237,097
Entity Common Stock, Shares Outstanding		198,506,718
Documents Incorporated by Reference [Text Block]	None
Entity Central Index Key	0000315293
Amendment Flag	true
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Description	This Amendment No. 1 on Form 10-K/A (this “Amendment”) amends our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, originally filed with the Securities and Exchange Commission (the “SEC”) on February 16, 2024 (the “Original Filing”). The Original Filing omitted Part III, Items 10 (Directors, Executive Officers and Corporate Governance), 11 (Executive Compensation), 12 (Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters), 13 (Certain Relationships and Related Transactions, and Director Independence) and 14 (Principal Accountant Fees and Services) in reliance on General Instruction G(3) to Form 10-K, which provides that such information may be either incorporated by reference from the registrant’s definitive proxy statement or included in an amendment to Form 10-K, in either case filed with the Securities and Exchange Commission (the “SEC”) not later than 120 days after the end of the fiscal year. We are filing this Amendment solely to amend Part III, Items 10, 11, 12, 13 and 14 of the Original Filing to include the information required by such Items.In addition, in connection with the filing of this Amendment and pursuant to the rules of the SEC, we are including with this Amendment new certifications of our principal executive officer and principal financial officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002. Item 15 of Part IV has also been amended to reflect the filing of these new certifications.Except as described above, no other changes have been made to the Original Filing. The Original Filing continues to speak as of the date of the Original Filing, and we have not updated the disclosures contained therein to reflect any events which occurred at a date subsequent to the filing of the Original Filing.Unless otherwise indicated or unless the context requires otherwise, all references in this Amendment to “we,” “us,” “our,” “our Company” or “the Company” refer to Aon plc, an Irish public limited company, together with its consolidated subsidiaries.As previously announced, on December 19, 2023, Aon entered into a definitive agreement with Randolph Acquisition Corp., a Delaware corporation and an indirect, wholly owned subsidiary of Aon (the “Acquirer”), Randolph Merger Sub LLC, a Delaware limited liability company and a direct, wholly owned subsidiary of the Acquirer, NFP Intermediate Holdings A Corp., a Delaware corporation (“NFP”), and NFP Parent Co, LLC, a Delaware limited liability company, pursuant to which the Acquirer will acquire NFP.
Capital Unit, Class A [Member]
Document Information [Line Items]
Title of 12(b) Security	Class A Ordinary Shares $0.01 nominal value
Trading Symbol	AON
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 3.50 Senior Notes Due 2024 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 3.50% Senior Notes due 2024
Trading Symbol	AON24
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 3.875 Senior Notes Due 2025 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 3.875% Senior Notes due 2025
Trading Symbol	AON25
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 2.875 Senior Notes Due 2026 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 2.875% Senior Notes due 2026
Trading Symbol	AON26
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.85 Senior Notes Due 2027 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.85% Senior Notes due 2027
Trading Symbol	AON27
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.05 Senior Notes Due 2031 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.05% Senior Notes due 2031
Trading Symbol	AON31
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.60 Senior Notes Due 2031 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.60% Senior Notes due 2031
Trading Symbol	AON31A
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 5.00 Senior Notes Due 2032 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.00% Senior Notes due 2032
Trading Symbol	AON32
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 5.35 Senior Notes Due 2033 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.35% Senior Notes due 2033
Trading Symbol	AON33
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 4.25 Senior Notes Due 2042 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.25% Senior Notes due 2042
Trading Symbol	AON42
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 4.45 Senior Notes Due 2043 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.45% Senior Notes due 2043
Trading Symbol	AON43
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 4.60 Senior Notes Due 2044 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.60% Senior Notes due 2044
Trading Symbol	AON44
Security Exchange Name	NYSE
Guarantees Of Aon Plcs 4.75 Senior Notes Due 2045 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.75% Senior Notes due 2045
Trading Symbol	AON45
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 2.90 Senior Notes Due 2051 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.90% Senior Notes due 2051
Trading Symbol	AON51
Security Exchange Name	NYSE
Guarantees Of Aon Corporation And Aon Global Holdings Plcs 3.90 Senior Notes Due 2052 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.90% Senior Notes due 2052
Trading Symbol	AON52
Security Exchange Name	NYSE
Guarantees of Aon North America Incs 5.125 Senior Notes due 2027 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027
Trading Symbol	AON27B
Security Exchange Name	NYSE
Guarantees of Aon North America Incs 5.150 Senior Notes due 2029 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029
Trading Symbol	AON29
Security Exchange Name	NYSE
Guarantees of Aon North America Incs 5.300 Senior Notes due 2031 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031
Trading Symbol	AON31B
Security Exchange Name	NYSE
Guarantees of Aon North America Incs 5.450 Senior Notes due 2034 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034
Trading Symbol	AON34
Security Exchange Name	NYSE
Guarantees of Aon North America Incs 5.750 Senior Notes due 2054 [Member]
Document Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054
Trading Symbol	AON54
Security Exchange Name	NYSE