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Unpaid losses and loss expenses Unpaid losses and loss expenses (narrative details) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse | [1] |  |  | $ (781) | $ (972)
prior period development, net adjustments |  |  |  | 110 | 75
North America Commercial P&C Insurance [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | $ (236) | $ (187) | (546) | (533)
North America Commercial P&C Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (242) | (167) | (431) | (473)
North America Commercial P&C Insurance [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 6 |  | (115) | (60)
North America Commercial P&C Insurance [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (99) | (134)
North America Commercial P&C Insurance [Member] | Multi-Line [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
prior period development, net adjustments |  | 26 |  |  |
North America Commercial P&C Insurance [Member] | Accident Year 2016 [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (37) |
North America Commercial P&C Insurance [Member] | Accident Year 2013 and prior [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (44) |  | (62) |
North America Commercial P&C Insurance [Member] | Accident years 2008 - 2013 [Member] | Commercial Multi-peril and General Liability [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (27) |
North America Commercial P&C Insurance [Member] | Accident years 2014 and 2016 [Member] | Property [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (43) |
North America Commercial P&C Insurance [Member] | Accident Year 2010 and Prior [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (127) |  | (272)
North America Commercial P&C Insurance [Member] | Accident year 2012 and 2013 [Member] | Professional Liability Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (30) |
North America Commercial P&C Insurance [Member] | Accident year 2012 and 2013 [Member] | Multi-Line [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (28) |  | (28) |
North America Commercial P&C Insurance [Member] | Accident year 2015 and 2016 [Member] | Accident and Health Insurance Product Line [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (19) |
North America Commercial P&C Insurance [Member] | Accident year 2011 and prior [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (140) |  | (213) |
North America Commercial P&C Insurance [Member] | Accident Year 2015 [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (40)
North America Commercial P&C Insurance [Member] | Accident Year 2015 [Member] | Credit Related Business [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (45) |
North America Commercial P&C Insurance [Member] | Accident year 2007 - 2014 [Member] | Primary Casualty GL [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (20)
North America Commercial P&C Insurance [Member] | Accident years 2012 and prior [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (91)
North America Commercial P&C Insurance [Member] | Accident years 2012 and prior [Member] | Professional Liability Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (69)
North America Commercial P&C Insurance [Member] | Accident year 2014 and 2015 [Member] | Property [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (20) |  | (46)
North America Personal P&C Insurance [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 32 | 38 | 66 | 20
North America Personal P&C Insurance [Member] | Personal Homeowner [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | 28 | 105 |
North America Personal P&C Insurance [Member] | Accident Year 2016 [Member] | Personal Homeowner [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 98 |  |  |
North America Personal P&C Insurance [Member] | Accident Year 2014 [Member] | Personal Excess [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (58) |  | (58) |
North America Agricultural Insurance [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (4) | (11) |  |
North America Agricultural Insurance [Member] | Commercial Multi-peril and General Liability [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (83) | (52)
Overseas General Insurance [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (108) | (223) | (184) | (338)
Overseas General Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (109) | (234) | (78) | (235)
Overseas General Insurance [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | 11 | (106) | (103)
Overseas General Insurance [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (40) |  | (9) |
Overseas General Insurance [Member] | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (167) |  | (167)
Overseas General Insurance [Member] | Individual Legacy Liability [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (25) |  |
Overseas General Insurance [Member] | Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (34) |  | (34) |
Overseas General Insurance [Member] | Accident Year 2013 and prior [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (69) |  |  |
Overseas General Insurance [Member] | Accident Year 2013 and prior [Member] | Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (124) |  |  |
Overseas General Insurance [Member] | Accident year 2013 to 2015 [Member] | Property and Inland Marine [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (37) |
Overseas General Insurance [Member] | Accident year 2013 to 2015 [Member] | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | 94 |  | 94
Overseas General Insurance [Member] | Accident years 2014 - 2016 [Member] | Accident and Health Insurance Product Line [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (20) |
Overseas General Insurance [Member] | Accident years 2014 - 2016 [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 29 |  |  |
Overseas General Insurance [Member] | Accident years 2014 - 2016 [Member] | Energy and Technical Risk Property [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (43) |
Overseas General Insurance [Member] | Accident years 2014 - 2016 [Member] | Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 90 |  |  |
Overseas General Insurance [Member] | Accident years 2012 and prior [Member] | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (261) |  | (261)
Overseas General Insurance [Member] | Accident years 2012 and prior [Member] | Aviation [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (28) |  |
Overseas General Insurance [Member] | Accident years 2016 and prior [Member] | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | 32 |
Overseas General Insurance [Member] | Accident year 2012 to 2014 [Member] | Property [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (66)
Overseas General Insurance [Member] | Accident year 2010 to 2014 [Member] | Energy and Technical Risk Property [Member] | Short Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (35)
Global Reinsurance [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (41) | (28) | (64) | (78)
Global Reinsurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (67) |
Global Reinsurance [Member] | Auto Liability Excess Lines [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | 10 |
Global Reinsurance [Member] | Accident Year 2013 and prior [Member] | Professional Liability Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | (29) |  | (66) |
Global Reinsurance [Member] | Accident year 2011 and prior [Member] | Professional Liability Insurance [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  | (24) |  | (30)
Global Reinsurance [Member] | Accident year 2011 and prior [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  |  | (41)
Global Reinsurance [Member] | Accident Year 2015 [Member] | Auto Liability Excess Lines [Member] | Long Tail [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | 9 |
Corporate Segment [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 87 | 62 | 140 | 84
Corporate Segment [Member] | Discontinued Operations [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | 9 | 10 | 28 | $ 27
Corporate Segment [Member] | non-A&E run-off [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  |  |  | $ 35 |
Corporate Segment [Member] | Asbestos & Environmental [Member] |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |
PPD (Favorable) / Adverse |  | $ 77 | $ 52 |  |
[1] | Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments, and earned premiums totaling $110 million and $75 million for the nine months ended September 30, 2017 and 2016, respectively.

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