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Business Segments (Revenues by Line of Business) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Total revenues | $ 11,908 | $ 10,808 | $ 10,767
Total operating revenues | 11,788 | 10,862 | 10,738
Net investment gains (losses) | 120 | (54) | 29
Operating Segments | Specialty |  |  |
Total revenues | 5,004 | 4,585 | 4,491
Operating Segments | Commercial |  |  |
Total revenues | 4,199 | 3,861 | 3,796
Operating Segments | International |  |  |
Total revenues | 1,114 | 998 | 1,037
Operating Segments | Life & Group |  |  |
Total revenues | 1,457 | 1,355 | 1,340
Operating Segments | Corporate & Other |  |  |
Total revenues | 21 | 69 | 81
Eliminations |  |  |
Total revenues | (7) | (6) | (7)
Management & Professional Liability | Operating Segments | Specialty |  |  |
Total revenues | 2,776 | 2,577 | 2,572
Surety | Operating Segments | Specialty |  |  |
Total revenues | 604 | 596 | 596
Warranty & Alternative Risks | Operating Segments | Specialty |  |  |
Total revenues | 1,624 | 1,412 | 1,323
Middle Market | Operating Segments | Commercial |  |  |
Total revenues | 1,508 | 1,444 | 1,439
Construction | Operating Segments | Commercial |  |  |
Total revenues | 1,322 | 1,120 | 1,043
Small Business | Operating Segments | Commercial |  |  |
Total revenues | 558 | 482 | 504
Other Commercial | Operating Segments | Commercial |  |  |
Total revenues | 811 | 815 | 810
Canada | Operating Segments | International |  |  |
Total revenues | 344 | 291 | 277
Europe | Operating Segments | International |  |  |
Total revenues | 473 | 389 | 363
Hardy | Operating Segments | International |  |  |
Total revenues | $ 297 | $ 318 | $ 397

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