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Reserve for Property and Casualty Insurance Claims and Claims Expense - Claims and allocated claim adjustment expenses, net of reinsurance (Details) $ in Millions | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) claim | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Increase (decrease) in claims and claims expense |  |  |  |  |
Liabilities for claims and claim adjustment expenses, net of recoverables | $ 20,577 |  |  |  |
Auto insurance - liability coverage |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 42,687 |  |  |  |
Prior year reserve reestimates | 7 |  |  |  |
Prior year reserve reestimates | 7 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | 31,287 |  |  |  |
All outstanding liabilities before 2016, net of recoverables | 1,389 |  |  |  |
Liabilities for claims and claim adjustment expenses, net of recoverables | 12,789 |  |  |  |
Auto insurance - liability coverage | Accident Year 2016 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 8,709 | $ 8,690 | $ 8,740 | $ 8,841 | $ 9,038
Prior year reserve reestimates | 19 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 554 |  |  |  |
Cumulative number of reported claims | claim | 2,400,904 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 8,155 | 7,700 | 6,853 | 5,772 | 3,487
Auto insurance - liability coverage | Accident Year 2017 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 8,330 | 8,312 | 8,396 | 8,465 |
Prior year reserve reestimates | 18 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 1,017 |  |  |  |
Cumulative number of reported claims | claim | 2,217,132 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 7,313 | 6,532 | 5,333 | 3,151 |
Auto insurance - liability coverage | Accident Year 2018 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 8,731 | 8,715 | 8,734 |  |
Prior year reserve reestimates | 16 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 1,846 |  |  |  |
Cumulative number of reported claims | claim | 2,180,275 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 6,885 | 5,618 | 3,231 |  |
Auto insurance - liability coverage | Accident Year 2019 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 9,295 | 9,341 |  |  |
Prior year reserve reestimates | (46) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 3,064 |  |  |  |
Cumulative number of reported claims | claim | 2,205,813 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 6,231 | 3,498 |  |  |
Auto insurance - liability coverage | Accident Year 2020 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 7,622 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 4,919 |  |  |  |
Cumulative number of reported claims | claim | 1,500,921 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 2,703 |  |  |  |
Auto insurance - liability coverage | Prior year reserve reestimates for pre-2016 accident years |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (20) |  |  |  |
Auto insurance - liability coverage | Prior year reserve reestimates for ULAE |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | 23 |  |  |  |
Auto insurance - physical damage coverage |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 25,687 |  |  |  |
Prior year reserve reestimates | (107) |  |  |  |
Prior year reserve reestimates | (114) |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | 25,322 |  |  |  |
All outstanding liabilities before 2016, net of recoverables | 8 |  |  |  |
Liabilities for claims and claim adjustment expenses, net of recoverables | 373 |  |  |  |
Auto insurance - physical damage coverage | Accident Year 2016 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 5,022 | 5,023 | 5,027 | 5,054 | 5,128
Prior year reserve reestimates | (1) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 5 |  |  |  |
Cumulative number of reported claims | claim | 4,432,048 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 5,017 | 5,018 | 5,022 | 5,033 | 4,890
Auto insurance - physical damage coverage | Accident Year 2017 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 5,027 | 5,028 | 5,039 | 5,121 |
Prior year reserve reestimates | (1) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 1 |  |  |  |
Cumulative number of reported claims | claim | 4,237,772 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 5,026 | 5,030 | 5,039 | 4,847 |
Auto insurance - physical damage coverage | Accident Year 2018 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 5,108 | 5,157 | 5,219 |  |
Prior year reserve reestimates | (49) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 9 |  |  |  |
Cumulative number of reported claims | claim | 4,310,750 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 5,099 | 5,140 | 4,971 |  |
Auto insurance - physical damage coverage | Accident Year 2019 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 5,606 | 5,662 |  |  |
Prior year reserve reestimates | (56) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 26 |  |  |  |
Cumulative number of reported claims | claim | 4,469,473 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 5,580 | 5,418 |  |  |
Auto insurance - physical damage coverage | Accident Year 2020 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 4,924 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 324 |  |  |  |
Cumulative number of reported claims | claim | 3,493,530 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 4,600 |  |  |  |
Auto insurance - physical damage coverage | Prior year reserve reestimates for pre-2016 accident years |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (1) |  |  |  |
Auto insurance - physical damage coverage | Prior year reserve reestimates for ULAE |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (5) |  |  |  |
Homeowners |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 22,859 |  |  |  |
Prior year reserve reestimates | (480) |  |  |  |
Prior year reserve reestimates | (439) |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | 20,874 |  |  |  |
All outstanding liabilities before 2016, net of recoverables | 119 |  |  |  |
Liabilities for claims and claim adjustment expenses, net of recoverables | 2,104 |  |  |  |
Homeowners | Accident Year 2016 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 3,948 | 3,953 | 3,958 | 3,995 | 3,961
Prior year reserve reestimates | (5) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 43 |  |  |  |
Cumulative number of reported claims | claim | 814,026 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 3,905 | 3,876 | 3,811 | 3,680 | $ 2,949
Homeowners | Accident Year 2017 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 4,390 | 4,614 | 4,619 | 4,477 |
Prior year reserve reestimates | (224) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 61 |  |  |  |
Cumulative number of reported claims | claim | 908,714 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 4,329 | 4,437 | 4,249 | $ 3,228 |
Homeowners | Accident Year 2018 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 4,551 | 4,854 | 4,749 |  |
Prior year reserve reestimates | (303) |  |  |  |
IBNR reserves plus expected development on reported claims | $ 182 |  |  |  |
Cumulative number of reported claims | claim | 811,046 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 4,369 | 4,514 | $ 3,491 |  |
Homeowners | Accident Year 2019 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 4,601 | 4,549 |  |  |
Prior year reserve reestimates | 52 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 301 |  |  |  |
Cumulative number of reported claims | claim | 784,257 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 4,300 | $ 3,316 |  |  |
Homeowners | Accident Year 2020 |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Incurred claims and allocated claim adjustment expenses, net of recoverables | 5,369 |  |  |  |
IBNR reserves plus expected development on reported claims | $ 1,398 |  |  |  |
Cumulative number of reported claims | claim | 838,829 |  |  |  |
Cumulative paid claims and allocated claims adjustment expenses, net of recoverables | $ 3,971 |  |  |  |
Homeowners | Prior year reserve reestimates for pre-2016 accident years |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (11) |  |  |  |
Homeowners | Prior year reserve reestimates for ULAE |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | 52 |  |  |  |
Other | Auto insurance - liability coverage |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (3) |  |  |  |
Other | Auto insurance - physical damage coverage |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | (1) |  |  |  |
Other | Homeowners |  |  |  |  |
Increase (decrease) in claims and claims expense |  |  |  |  |
Prior year reserve reestimates | $ 0 |  |  |  |

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