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Condensed Financial Information of Registrant (Schedule Of Condensed Financial Information Of Registrant, Statements Of Cash Flow) (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Cash flows from operating activities: |  |  |
Net cash provided by operating activities | $ 605,616,000 | $ 519,678,000 | $ 383,434,000
Cash flows from investing activities: |  |  |
Capital distribution from subsidiaries | 12,100,000 | 5,200,000 |
Equity securities available for sale in nature |  |  |
Purchases | (1,230,785,000) | (1,174,759,000) | (1,026,827,000)
Sales | 1,174,540,000 | 1,088,701,000 | 954,755,000
Other, net | 20,577,000 | 6,247,000 | 10,105,000
Net cash used in investing activities | (411,286,000) | (401,201,000) | (222,436,000)
Cash flows from financing activities: |  |  |
Dividends paid to shareholders | (139,640,000) | (139,071,000) | (138,478,000)
Proceeds from stock options exercised | 0 | 701,000 | 358,000
Net cash used in financing activities | (140,249,000) | (138,370,000) | (138,120,000)
Net (decrease) increase in cash | 54,081,000 | (19,893,000) | 22,878,000
Cash: |  |  |
Beginning of year | 294,398,000 | 314,291,000 | 291,413,000
End of year | 348,479,000 | 294,398,000 | 314,291,000
SUPPLEMENTAL CASH FLOW DISCLOSURE |  |  |
Interest paid | 16,599,000 | 16,586,000 | 16,586,000
Income taxes (refunded) paid, net | 52,659,000 | (14,564,000) | (10,989,000)
Parent Company [Member] |  |  |
Cash flows from operating activities: |  |  |
Net cash provided by operating activities | (17,339,000) | (5,392,000) | (16,108,000)
Cash flows from investing activities: |  |  |
Capital contribution to subsidiaries | (30,000,000) | (125,000) | (540,619)
Capital distribution from subsidiaries | 0 | 30,068,567 | 0
Distributions received from special purpose entities | 12,129,000 | 5,153,000 | 5,998,000
Dividends received from subsidiaries | 121,000,000 | 114,431,000 | 135,000,000
Equity securities available for sale in nature |  |  |
Purchases | (54,571,000) | (39,966,000) | (22,286,000)
Sales | 67,965,000 | 74,663,000 | 33,052,000
Decrease (increase) in short-term investments | 25,088,000 | (25,213,000) | 18,065,000
Other, net | 254,000 | 376,000 | 605,000
Net cash used in investing activities | 141,865,000 | 159,388,000 | 169,893,000
Cash flows from financing activities: |  |  |
Dividends paid to shareholders | (139,640,000) | (139,071,000) | (138,478,000)
Proceeds from stock options exercised | 0 | 701,000 | 358,000
Net cash used in financing activities | (139,640,000) | (138,370,000) | (138,120,000)
Net (decrease) increase in cash | (15,114,000) | 15,626,000 | 15,665,000
Cash: |  |  |
Beginning of year | 39,766,000 | 24,140,000 | 8,475,000
End of year | 24,652,000 | 39,766,000 | 24,140,000
SUPPLEMENTAL CASH FLOW DISCLOSURE |  |  |
Interest paid | 16,586,000 | 16,586,000 | 16,586,000
Income taxes (refunded) paid, net | $ (20,552,000) | $ (12,391,000) | $ 4,296,000

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