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Investments (Unrealized Gains on Investments) (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Net unrealized gains | $ 228,963 | $ 386,393 | $ 215,688 |
Deferred income tax expense | (48,082) | (81,142) | (45,294) |
Net unrealized gains, net of deferred income tax | 180,881 | 305,251 | 170,394 |
Total stockholders’ equity | 2,982,885 | 2,738,889 | 2,194,936 |
Increase (decrease) in net unrealized gains in OCI, net of deferred income tax | (124,370) | (134,857) | (168,505) |
Available-for-sale Securities [Member] |  |  |  |
Net unrealized gains | 228,947 | 386,380 | 215,634 |
Total HTM Securities [Member] |  |  |  |
Net unrealized gains | (4) | 7 | 31 |
Short-term Investments [Member] |  |  |  |
Net unrealized gains | 20 | 6 | 23 |
Retained Earnings [Member] |  |  |  |
Total stockholders’ equity | $ 2,603,472 | $ 2,271,537 | $ 2,080,529 | $ 1,858,414

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