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Unpaid losses and loss expenses Unpaid losses and loss expenses (narrative details) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  | $ (461) | $ (601)
North America Commercial P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | $ (131) | $ (168) | (310) | (346)
North America Commercial P&C Insurance [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (101) | (167) | (200) | (309)
North America Commercial P&C Insurance [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (30) |  | (110) | (37)
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 | (83) | (114) | (84) | (114)
North America Commercial P&C Insurance [Member] | Primary casualty GL [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  | (24) |
North America Commercial P&C Insurance [Member] | construction defects [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  |  | 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 | (57) |  |  |
North America Commercial P&C Insurance [Member] | Accident Year 2015 and prior [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 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 | (37) |  | (37) |
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 |  |  | (33) |
North America Commercial P&C Insurance [Member] | Accident years 2014 - 2016 [Member] | Commercial Property [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (29) |  |  |
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 |  |  | (74) | (145)
North America Commercial P&C Insurance [Member] | Accident year 2012 and 2013 [Member] | Professional Malpractice Liability Insurance [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  | (25) |
North America Commercial P&C Insurance [Member] | Accident year 2011 and prior [Member] | North America Workers' Compensation [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  | (59) |  |
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 |  |  | (24) |
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] | Commercial Multi-peril and General Liability [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  | (50) |  | (50)
North America Commercial P&C Insurance [Member] | Accident year 2003 [Member] | Professional Malpractice Liability Insurance [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] | Professional Malpractice Liability Insurance [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (63)
North America Commercial P&C Insurance [Member] | Accident Year 2013 [Member] | Credit related business [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  |  | (24)
North America Personal P&C Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | 37 | (15) | 34 | (18)
North America Agricultural Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | 0 | 0 | (79) | (41)
Overseas General Insurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (88) | (85) | (76) | (115)
Overseas General Insurance [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (88) | (84) | (108) |
Overseas General Insurance [Member] | Energy and Technical Risk Property [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  | (32) |  |
Overseas General Insurance [Member] | Accident year 2013 to 2015 [Member] | Property [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  | (38) |  |
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 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 | (26) |  |  |
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 | (19) |  |  |
Overseas General Insurance [Member] | Accident years 2016 and prior [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  | 32 |
Global Reinsurance [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (31) | (47) | (23) | (50)
Global Reinsurance [Member] | Casualty & Professional [Member] | Long Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse |  |  | (27) |
Global Reinsurance [Member] | Accident year 2011 and prior [Member] | Casualty & Professional [Member] | Short Tail [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | (36) |  |  |
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 | 43 | $ 14 | 53 | $ 22
Corporate Segment [Member] | Discontinued Operations [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | 8 |  | $ 18 |
Corporate Segment [Member] | non-A&E run-off [Member] |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
PPD (Favorable) / Adverse | $ 35 |  |  |

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