XML 99 R81.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Shareholders' Equity - Ordinary Shares (Details) - USD ($) $ / shares in Units, shares in Thousands | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jan. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Feb. 28, 2017 | Nov. 30, 2014 | Apr. 30, 2012
Common Stock Programs |  |  |  |  |  |  |
Cost of shares repurchased |  | $ 2,415,000,000 | $ 1,257,000,000 | $ 1,550,000,000 |  |  |
Additional transaction costs |  | $ 12,000,000 | $ 6,000,000 |  |  |  |
Share Repurchase Program of 2012 |  |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |  |
Share repurchase authorization limit |  |  |  |  |  |  | $ 5,000,000,000.0
Number of shares repurchased (in shares) |  | 108,200 |  |  |  |  |
Cost of shares repurchased |  | $ 9,600,000,000 |  |  |  |  |
Share Repurchase Program of 2014 |  |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |  |
Share repurchase authorization limit |  | $ 15,000,000,000.0 |  |  | $ 5,000,000,000.0 | $ 5,000,000,000.0 |
Share Repurchase Program |  |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |  |
Number of shares repurchased (in shares) |  | 18,000 | 12,200 |  |  |  |
Average price per share of shares purchased under share repurchase program (in dollars per share) |  | $ 133.67 | $ 102.66 |  |  |  |
Cost of shares repurchased |  | $ 2,400,000,000 | $ 1,300,000,000 |  |  |  |
Share Repurchase Programs of 2012 and 2014 |  |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |  |
Share repurchase, remaining authorization limit |  | $ 5,400,000,000 |  |  |  |  |
Subsequent Event | Share Repurchase Program |  |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |  |
Number of shares repurchased (in shares) | 118 |  |  |  |  |  |
Average price per share of shares purchased under share repurchase program (in dollars per share) | $ 134.41 |  |  |  |  |  |
Cost of shares repurchased | $ 15,900,000 |  |  |  |  |  |

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | aon_CommonStockProgramsLineItems
Namespace Prefix: | aon_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Treasury Stock, Acquired, Additional Transaction Costs + References No definition available. + Details
Name: | aon_TreasuryStockAcquiredAdditionalTransactionCosts
Namespace Prefix: | aon_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
Name: | us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: 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(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 + Details
Name: | us-gaap_TreasuryStockSharesAcquired
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
Name: | us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_ShareRepurchaseProgramAxis=aon_ShareRepurchaseProgramOf2012Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareRepurchaseProgramAxis=aon_ShareRepurchaseProgramof2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareRepurchaseProgramAxis=aon_ShareRepurchaseProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShareRepurchaseProgramAxis=aon_ShareRepurchaseProgramsof2012and2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |