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Unpaid losses and loss expenses (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2004
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | $ 108 | $ 69 | $ 0 |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (829) | $ (1,135) | $ (546) |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 1.70% | 2.40% | 2.00% |  |  |  |
Incurred activity |  | $ 18,454 | $ 16,052 | $ 9,484 |  |  |  |
Liability for Claims and Claims Adjustment Expense |  | 63,179 | 60,540 | 37,303 | $ 38,315 |  |  |
Brandywine Run-off [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Incurred activity |  | 672 |  |  |  |  |  |
Reinsurance coverage to Century provided by ACE INA under XOL |  | 800 |  |  |  |  |  |
Statutory capital and surplus |  | 25 |  |  |  |  |  |
Dividend retention fund established by INA Financial Corporation |  | 50 |  |  |  |  |  |
Required minimum balance under the dividend retention fund |  | 50 |  |  |  |  |  |
Contributions to the dividend retention fund |  | 49 |  |  |  | $ 35 | $ 15 |
Minimum contribution from the dividend retention fund to Century not required for XOL agreement |  | 200 |  |  |  |  |  |
Aggregate reinsurance balances ceded by active ACE companies to Century |  | 1,400 | 1,200 |  |  |  |  |
Liability for Claims and Claims Adjustment Expense |  | $ 2,000 |  |  |  |  |  |
Surplus note |  |  |  |  |  |  |  | $ 100
Westchester and Brandywine Run-off [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
NICO pro-rata share of reinsurance protection (percent) |  | 75.00% |  |  |  |  |  |
NICO retention for losses and loss expenses incurred on or before 12/31/1996 |  | $ 721 |  |  |  |  |  |
NICO reinsurance protection on losses and loss expenses incurred on or before 12/31/1996, net of retenion |  | 1,000 |  |  |  |  |  |
NICO reinsurance protection on losses and loss expenses |  | 409 |  |  |  |  |  |
Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
PPD adjustments |  |  | (101) | (46) |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (423) | (817) | (263) |  |  |  |
Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (406) | (318) | (283) |  |  |  |
North America Commercial P&C Insurance |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 57 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (746) | $ (778) | $ (264) |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 1.60% | 1.60% | 1.00% |  |  |  |
North America Commercial P&C Insurance | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | $ 56 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (562) | $ (693) | $ (162) |  |  |  |
North America Commercial P&C Insurance | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 1 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (184) | (85) | (102) |  |  |  |
North America Commercial P&C Insurance | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (123) | (141) |  |  |  |  |
North America Commercial P&C Insurance | Commercial Excess and Umbrella [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (184) |  |  |  |  |  |
North America Commercial P&C Insurance | 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 | Management Liability [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (181) |  |  |  |  |  |
North America Commercial P&C Insurance | 2011 and prior [Member] | Directors and Officers Liability Insurance [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (220) |  |  |  |  |
North America Commercial P&C Insurance | Accident Year 2010 and Prior [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (264) |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2015 and 2016 [Member] | Accident and Health [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (20) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2015 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (40) |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2015 [Member] | Surety [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (45) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident Year 2016 [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (57) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident years 2012 and prior [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (92) |  |  |  |  |
North America Commercial P&C Insurance | Accident years 2012 and prior [Member] | Professional Errors and Omissions Insurance [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (58) |  |  |  |  |
North America Commercial P&C Insurance | Accident Year 2013 and prior [Member] | North America Commercial P&C Insurance - Workers' Compensation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (65) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2012 and 2013 [Member] | Professional Errors and Omissions Insurance [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (32) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2012 and 2013 [Member] | Multi-Line [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (28) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2013 [Member] | Auto Liability Excess Lines [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 21 |  |  |  |  |  |
North America Commercial P&C Insurance | Accident year 2013 [Member] | Political [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (21) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident Years 2012 - 2016 [Member] | Property and Inland Marine [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (98) |  |  |  |  |  |
North America Commercial P&C Insurance | Accident Year 2012 [Member] | Political [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (21) |  |  |  |  |
North America Personal P&C Insurance [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 69 | $ 27 | $ 25 |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 0.10% | 0.10% | 0.10% |  |  |  |
North America Personal P&C Insurance [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 0 | $ 0 | $ 0 |  |  |  |
North America Personal P&C Insurance [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 0 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 69 | 27 | 25 |  |  |  |
North America Personal P&C Insurance [Member] | Accident Year 2014 [Member] | Personal Excess [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (58) |  |  |  |  |  |
North America Personal P&C Insurance [Member] | Accident years 2013 and 2016 [Member] | Personal homeowner [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 105 |  |  |  |  |  |
North America Agricultural Insurance |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (119) | $ (72) | $ (45) |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 0.20% | 0.20% | 0.10% |  |  |  |
North America Agricultural Insurance | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 0 | $ 0 | $ 0 |  |  |  |
North America Agricultural Insurance | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 55 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (119) | (72) | (45) |  |  |  |
Overseas General Insurance |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 0 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (252) | $ (423) | $ (343) |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 0.50% | 0.90% | 1.30% |  |  |  |
Overseas General Insurance | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | $ 0 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (71) | $ (236) | $ (192) |  |  |  |
Overseas General Insurance | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | 0 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (181) | (187) | (151) |  |  |  |
Overseas General Insurance | Financial [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (34) |  |  |  |  |  |
Overseas General Insurance | Casualty [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (10) |  |  |  |  |  |
Overseas General Insurance | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (177) |  |  |  |  |
Overseas General Insurance | Individual Legacy Liability [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (25) |  |  |  |  |
Overseas General Insurance | Accident year 2015 and 2016 [Member] | Marine [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (42) |  |  |  |  |  |
Overseas General Insurance | Accident years 2012 and prior [Member] | Casualty and Financial [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (266) |  |  |  |  |
Overseas General Insurance | Accident years 2012 and prior [Member] | Aviation [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (28) |  |  |  |  |
Overseas General Insurance | Accident year 2013 - 2015 [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | 89 |  |  |  |  |
Overseas General Insurance | Accident year 2013 - 2015 [Member] | Property [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (25) |  |  |  |  |  |
Overseas General Insurance | Accident year 2013 - 2015 [Member] | Accident and Health [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (28) |  |  |  |  |
Overseas General Insurance | Accident year 2012 - 2014 [Member] | Property [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (97) |  |  |  |  |
Overseas General Insurance | Accident year 2010 - 2014 [Member] | Energy [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (43) |  |  |  |  |
Overseas General Insurance | Accident Year 2013 and prior [Member] | Financial [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (124) |  |  |  |  |  |
Overseas General Insurance | Accident Year 2013 and prior [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (69) |  |  |  |  |  |
Overseas General Insurance | Accident years 2016 and prior [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 32 |  |  |  |  |  |
Overseas General Insurance | Accident years 2014 - 2016 [Member] | Financial [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 90 |  |  |  |  |  |
Overseas General Insurance | Accident years 2014 - 2016 [Member] | Casualty [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 27 |  |  |  |  |  |
Overseas General Insurance | Accident years 2014 - 2016 [Member] | Energy and Technical Risk Property [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (43) |  |  |  |  |  |
Overseas General Insurance | Accident years 2014 - 2016 [Member] | Accident and Health [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (48) |  |  |  |  |  |
Overseas General Insurance - Non-Casualty [Member] | Latin America [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Loss by Geographic Percentage |  | 35.00% |  |  |  |  |  |
Global Reinsurance |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (59) | $ (78) | $ (119) |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 0.10% | 0.20% | 0.40% |  |  |  |
Global Reinsurance | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ (68) | $ (77) | $ (109) |  |  |  |
Global Reinsurance | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 9 | (1) | (10) |  |  |  |
Global Reinsurance | Auto Liability Excess Lines [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 10 |  |  |  |  |  |
Global Reinsurance | 2011 and prior [Member] | Casualty and Financial [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (42) |  |  |  |  |
Global Reinsurance | 2011 and prior [Member] | Professional Liability [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  |  | (30) |  |  |  |  |
Global Reinsurance | Accident Year 2013 and prior [Member] | Casualty [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | (67) |  |  |  |  |  |
Global Reinsurance | Accident Year 2015 and prior [Member] | Auto Liability Excess Lines [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 9 |  |  |  |  |  |
Global Reinsurance | UNITED STATES | Accident year 2008 and after [Member] | Non-catastrophe [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Loss by Geographic Percentage |  | 72.00% |  |  |  |  |  |
Global Reinsurance | UNITED STATES | Accident years 2008 to 2012 [Member] | Non-catastrophe [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Loss by Geographic Percentage |  | 60.00% |  |  |  |  |  |
Global Reinsurance | UNITED STATES | Accident years 2013 - 2017 [Member] | Non-catastrophe [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Loss by Geographic Percentage |  | 84.00% |  |  |  |  |  |
Corporate Segment [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 278 | $ 189 | $ 200 |  |  |  |
Prior Period Development Percentage Opening Net Unpaid Reserves | [1] | 0.60% | 0.40% | 0.70% |  |  |  |
Corporate Segment [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
prior period development, net adjustments |  | $ 0 |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 278 | $ 189 | $ 200 |  |  |  |
Corporate Segment [Member] | Long Tail [Member] | Discontinued Operations [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 39 | 48 |  |  |  |  |
Corporate Segment [Member] | Short Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | 0 | 0 | $ 0 |  |  |  |
Corporate Segment [Member] | Asbestos & Environmental [Member] | Long Tail [Member] |  |  |  |  |  |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |  |  |  |  |
Prior Year Claims and Claims Adjustment Expense |  | $ 239 | $ 141 |  |  |  |  |
[1] | (1) Calculated based on the beginning of period consolidated net unpaid losses and loss expenses. For 2016, the percent of beginning net unpaid reserves is calculated inclusive of the net unpaid losses and loss expenses acquired in the Chubb Corp acquisition of $21.4 billion.

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