XML 106 R91.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Shareholders' Equity - Components of Accumulated other comprehensive loss, net of related tax (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Jan. 01, 2018 | Jan. 01, 2017
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |  |
Beginning Balance | $ 4,648 | $ 5,532 | $ 6,059 |  |
Adoption of new accounting guidance |  |  |  | $ 492 | $ 49
Adjusted Beginning Balance |  |  |  | 5,140 | $ 5,581
Other comprehensive income (loss) before reclassifications | (576) | 195 | (791) |  |
Tax benefit (expense) | 43 | 47 | 77 |  |
Other comprehensive income (loss) before reclassifications, net | (533) | 242 | (714) |  |
Amounts reclassified from accumulated other comprehensive income (loss) | 157 | 227 | 332 |  |
Tax benefit (expense) | (36) | (53) | (107) |  |
Amounts reclassified from accumulated other comprehensive income (loss), net | 121 | 174 | 225 |  |
Total other comprehensive income (loss) attributable to Aon shareholders | (412) | 416 | (489) |  |
Ending Balance | 4,219 | 4,648 | 5,532 |  |
Change in Fair Value of Investments |  |  |  |  |
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |  |
Beginning Balance | (25) | (37) | (25) |  |
Adoption of new accounting guidance |  |  |  | (1) |
Adjusted Beginning Balance |  |  |  | (26) |
Other comprehensive income (loss) before reclassifications | (15) | 18 | (25) |  |
Tax benefit (expense) | 18 | (3) | 6 |  |
Other comprehensive income (loss) before reclassifications, net | 3 | 15 | (19) |  |
Amounts reclassified from accumulated other comprehensive income (loss) | 11 | (2) | 10 |  |
Tax benefit (expense) | (3) | (1) | (3) |  |
Amounts reclassified from accumulated other comprehensive income (loss), net | 8 | (3) | 7 |  |
Total other comprehensive income (loss) attributable to Aon shareholders | 11 | 12 | (12) |  |
Ending Balance | (15) | (25) | (37) |  |
Foreign Currency Translation Adjustments |  |  |  |  |
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |  |
Beginning Balance | (879) | (1,264) | (771) |  |
Adoption of new accounting guidance |  |  |  | 0 |
Adjusted Beginning Balance |  |  |  | (879) |
Other comprehensive income (loss) before reclassifications | (437) | 397 | (490) |  |
Tax benefit (expense) | (3) | (5) | (3) |  |
Other comprehensive income (loss) before reclassifications, net | (440) | 392 | (493) |  |
Amounts reclassified from accumulated other comprehensive income (loss) | 0 | (7) | 0 |  |
Tax benefit (expense) |  | 0 | 0 |  |
Amounts reclassified from accumulated other comprehensive income (loss), net | 0 | (7) | 0 |  |
Total other comprehensive income (loss) attributable to Aon shareholders | (440) | 385 | (493) |  |
Ending Balance | (1,319) | (879) | (1,264) |  |
Post-retirement Benefit Obligations |  |  |  |  |
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |  |
Beginning Balance | (2,592) | (2,611) | (2,627) |  |
Adoption of new accounting guidance |  |  |  | 0 |
Adjusted Beginning Balance |  |  |  | (2,592) |
Other comprehensive income (loss) before reclassifications | (124) | (220) | (276) |  |
Tax benefit (expense) | 28 | 55 | 74 |  |
Other comprehensive income (loss) before reclassifications, net | (96) | (165) | (202) |  |
Amounts reclassified from accumulated other comprehensive income (loss) | 146 | 236 | 322 |  |
Tax benefit (expense) | (33) | (52) | (104) |  |
Amounts reclassified from accumulated other comprehensive income (loss), net | 113 | 184 | 218 |  |
Total other comprehensive income (loss) attributable to Aon shareholders | 17 | 19 | 16 |  |
Ending Balance | (2,575) | (2,592) | (2,611) |  |
AOCI Including Portion Attributable to Noncontrolling Interest |  |  |  |  |
Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] |  |  |  |  |
Beginning Balance | (3,496) | (3,912) | (3,423) |  |
Adoption of new accounting guidance |  |  |  | (1) |
Adjusted Beginning Balance |  |  |  | $ (3,497) |
Ending Balance | $ (3,909) | $ (3,496) | $ (3,912) |  |

X
- Definition Changes in Accumulated Other Comprehensive Income (Loss) [Roll Forward] + References No definition available. + Details
Name: | aon_ChangesInAccumulatedOtherComprehensiveIncomeLossRollForward
Namespace Prefix: | aon_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before tax and reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after tax, before reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669625-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569643-111683 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669619-108580 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569616-111683 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e39076-109324 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount before tax of reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 17B -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL34724394-108580 + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 17B -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL34724394-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=109228884&loc=d3e1436-108581 + Details
Name: | us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 17A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL34724391-108580 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e39076-109324 + Details
Name: | us-gaap_ReclassificationFromAociCurrentPeriodTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568740-111683 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4I -URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4590271-111686 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4568447-111683 + Details
Name: | us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of stockholders' equity including the portion attributable to noncontrolling interests, after the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedTranslationAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |