Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions |
Total |
Reclassification out of Accumulated Other Comprehensive Loss [Member] |
Preferred Stock [Member] |
Common Stock [Member] |
Additional Paid-in Capital [Member] |
Net Unrealized Appreciation (Depreciation) on Investments [Member] |
Net Unrealized Appreciation (Depreciation) on Investments [Member]
Reclassification out of Accumulated Other Comprehensive Loss [Member]
|
Defined Benefit Pension and Postretirement Plans [Member] |
Defined Benefit Pension and Postretirement Plans [Member]
Reclassification out of Accumulated Other Comprehensive Loss [Member]
|
Long Duration Insurance Contracts [Member] |
Retained Earnings [Member] |
Retained Earnings [Member]
Adjustment [Member]
|
Retained Earnings [Member]
Adjusted Balance [Member]
|
Accumulated Other Comprehensive Income (Loss), Net of Tax [Member] |
Treasury Stock [Member] |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Balance at beginning of period at Dec. 31, 2024 | $ 0.0 | $ 0.6 | $ 1,973.6 | $ (403.5) | $ (55.2) | $ 2.4 | $ 3,209.6 | $ 1.9 | $ 3,211.5 | $ (1,885.7) | |||||
| Net income | $ 285.3 | $ (20.9) | $ (18.4) | 285.3 | |||||||||||
| Shares purchased at cost | (38.6) | ||||||||||||||
| Employee and director stock-based awards and other | 20.3 | ||||||||||||||
| Net appreciation (depreciation) on available-for-sale securities | 167.5 | 167.5 | |||||||||||||
| Income from continuing operations | 285.1 | $ 2.7 | |||||||||||||
| Net change in market risk | (1.1) | (1.1) | |||||||||||||
| Dividends to shareholders | (65.6) | ||||||||||||||
| Net shares reissued at cost under employee stock-based compensation plans and other | 2.1 | ||||||||||||||
| Balance at end of period at Jun. 30, 2025 | 3,216.3 | 1,993.9 | (236.0) | (52.5) | 1.3 | 3,431.2 | $ (287.2) | (1,922.2) | |||||||
| Balance at beginning of period at Mar. 31, 2025 | 0.0 | 0.6 | 1,978.3 | (292.3) | (53.8) | 1.4 | 3,306.8 | 0.0 | 3,306.8 | (1,896.6) | |||||
| Net income | 157.1 | (5.1) | (3.8) | 157.1 | |||||||||||
| Shares purchased at cost | (27.6) | ||||||||||||||
| Employee and director stock-based awards and other | 15.6 | ||||||||||||||
| Net appreciation (depreciation) on available-for-sale securities | 56.3 | 56.3 | |||||||||||||
| Income from continuing operations | 156.9 | 1.3 | |||||||||||||
| Net change in market risk | (0.1) | (0.1) | |||||||||||||
| Dividends to shareholders | (32.7) | ||||||||||||||
| Net shares reissued at cost under employee stock-based compensation plans and other | 2.0 | ||||||||||||||
| Balance at end of period at Jun. 30, 2025 | 3,216.3 | 1,993.9 | (236.0) | (52.5) | 1.3 | 3,431.2 | (287.2) | (1,922.2) | |||||||
| Balance at beginning of period at Dec. 31, 2025 | 3,571.5 | 0.0 | 0.6 | 2,013.5 | (116.3) | (54.3) | (0.8) | 3,741.6 | 0.0 | 3,741.6 | (2,012.8) | ||||
| Net income | 378.4 | (12.5) | (10.2) | 378.4 | |||||||||||
| Shares purchased at cost | (142.9) | ||||||||||||||
| Employee and director stock-based awards and other | 18.5 | ||||||||||||||
| Net appreciation (depreciation) on available-for-sale securities | (87.6) | (87.6) | |||||||||||||
| Income from continuing operations | 378.2 | 2.7 | |||||||||||||
| Net change in market risk | 0.6 | 0.6 | |||||||||||||
| Dividends to shareholders | (67.5) | ||||||||||||||
| Net shares reissued at cost under employee stock-based compensation plans and other | (1.2) | ||||||||||||||
| Balance at end of period at Jun. 30, 2026 | 3,672.5 | 2,032.0 | (203.9) | (51.6) | (0.2) | 4,052.5 | (255.7) | (2,156.9) | |||||||
| Balance at beginning of period at Mar. 31, 2026 | $ 0.0 | $ 0.6 | 2,016.0 | (185.2) | (52.9) | 0.2 | 3,894.5 | $ 0.0 | $ 3,894.5 | (2,102.8) | |||||
| Net income | 191.6 | $ (6.4) | $ (5.3) | 191.6 | |||||||||||
| Shares purchased at cost | (55.4) | ||||||||||||||
| Employee and director stock-based awards and other | 16.0 | ||||||||||||||
| Net appreciation (depreciation) on available-for-sale securities | (18.7) | (18.7) | |||||||||||||
| Income from continuing operations | 191.4 | $ 1.3 | |||||||||||||
| Net change in market risk | (0.4) | (0.4) | |||||||||||||
| Dividends to shareholders | (33.6) | ||||||||||||||
| Net shares reissued at cost under employee stock-based compensation plans and other | 1.3 | ||||||||||||||
| Balance at end of period at Jun. 30, 2026 | $ 3,672.5 | $ 2,032.0 | $ (203.9) | $ (51.6) | $ (0.2) | $ 4,052.5 | $ (255.7) | $ (2,156.9) |