Debt, Number Of Committed Credit Facilities

No definition available.

Name:	aon_DebtNumberOfCommittedCreditFacilities
Namespace Prefix:	aon_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the calculation as of the balance sheet date of the average interest rate weighted by the average outstanding amount of short-term debt outstanding by type or by instrument at that time.

+ References

No definition available.

+ Details

Name:	aon_ShortTermDebtAverageOutstandingAmountWeightedAverageInterestRate
Namespace Prefix:	aon_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

Name:	us-gaap_ExtinguishmentOfDebtAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For the form of debt having an initial term of less than one year or less than the normal operating cycle, if longer, average borrowings during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ShorttermDebtAverageOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Debt - Narrative (Details) CAD in Millions	3 Months Ended	12 Months Ended
Debt - Narrative (Details) CAD in Millions	Sep. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) credit_facility	Dec. 31, 2015 USD ($)	Dec. 31, 2016 CAD	Dec. 31, 2016 EUR (€)	May 27, 2016 USD ($)	Mar. 01, 2016 USD ($)	Nov. 13, 2015 USD ($)	May 20, 2015 USD ($)
Debt Instrument [Line Items]
Number of committed credit facilities \| credit_facility		2
Weighted average commercial paper outstanding		$ 265,000,000	$ 402,000,000
Senior Notes \| 3.125% Senior Notes due May 2016
Debt Instrument [Line Items]
Debt face value						$ 500,000,000
Interest rate on debt		3.125%		3.125%	3.125%
Senior Notes \| 3.875% Senior Notes due December 2025
Debt Instrument [Line Items]
Debt face value							$ 750,000,000
Interest rate on debt		3.875%		3.875%	3.875%
Senior Notes \| 2.80% Senior Notes due March 2021
Debt Instrument [Line Items]
Debt face value								$ 400,000,000
Interest rate on debt		2.80%		2.80%	2.80%
Senior Notes \| 4.75% Senior Notes due May 2045
Debt Instrument [Line Items]
Debt face value									$ 600,000,000
Interest rate on debt		4.75%		4.75%	4.75%
Senior Notes \| 4.76% Senior Notes due March 2018 (CAD 375M)
Debt Instrument [Line Items]
Debt face value \| CAD				CAD 375
Interest rate on debt		4.76%		4.76%	4.76%
Unsecured Debt \| 4.76% Senior Notes due March 2018 (CAD 375M)
Debt Instrument [Line Items]
Interest rate on debt		4.76%		4.76%	4.76%
Commercial Paper
Debt Instrument [Line Items]
Weighted-average interest rates		0.22%	0.50%
Senior Notes \| 3.50% Senior Notes due September 2015
Debt Instrument [Line Items]
Interest rate on debt	3.50%
Extinguishment of debt	$ 600,000,000
Credit Facility Expiring March 2017
Debt Instrument [Line Items]
New credit and loan facility		$ 400,000,000
Long-term commercial paper		0
Credit Facility Expiring February 2021
Debt Instrument [Line Items]
New credit and loan facility		900,000,000
Long-term commercial paper		0
Commercial Paper \| Line of Credit
Debt Instrument [Line Items]
Long-term commercial paper		329,200,000	$ 50,000,000
Commercial Paper \| US Commercial Paper Program
Debt Instrument [Line Items]
New credit and loan facility		$ 900,000,000
Commercial Paper \| European Multi-Currency Commercial Paper Program
Debt Instrument [Line Items]
New credit and loan facility \| €					€ 300,000,000