Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Statement Of Cash Flows [Abstract]
Net cash provided by operating activities	$ 342,192	$ 282,886
Purchase of:
Fixed income securities, available-for-sale	(560,192)	(531,894)
Equity securities	(40,571)	(42,490)
Property and equipment	(5,451)	(4,432)
Other	(8,535)	(7,940)
Proceeds from sale of:
Fixed income securities - available-for-sale	26,158	46,448
Equity securities	36,708	59,264
Equity method investments	14,134	686,666
Other	550	2,298
Proceeds from call or maturity of:
Fixed income securities - available-for-sale	414,529	176,616
Net proceeds from sale (purchase) of short-term investments	(88,803)
Net cash provided by (used in) investing activities	(211,473)	384,536
Cash Flows from Financing Activities
Proceeds from issuance of debt	50,000
Payment of debt	(150,000)
Cash dividends paid	(36,490)	(34,913)
Proceeds from stock option exercises	1,398	2,198
Net cash used in financing activities	(135,092)	(32,715)
Net increase (decrease) in cash	(4,373)	634,707
Cash at the beginning of the period	22,818	88,804
Cash at September 30	$ 18,445	$ 723,511

Cash inflow (outflow) from stock option exercises.

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Represents the amount of net cash outflow from other investing activities.

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Payments to Acquire Investments and Productive Assets [Abstract]

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Represents the amount of net cash inflow (outflow) from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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Proceeds from Sale of Investments and Productive Assets [Abstract]

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of increase (decrease) in cash, cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; including effect from exchange rate change. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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The cash outflow for the settlement of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, as it matures.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The net amount paid (received) by the reporting entity through acquisition or sale and maturities of short-term investments with an original maturity that is three months or less which qualify for treatment as an investing activity based on management's intention and intended by management to be liquidated, if necessary, within the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the short-term.

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Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

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Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of cash outflow for purchase of marketable security.

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The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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Amount of cash inflow from maturity, prepayment and call of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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