Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Condensed Consolidated Statements of Cash Flows
Net Cash Provided by Operating Activities	$ 163,369	$ 145,933
Net Cash Provided by (Used in) Investing Activities [Abstract]
Investments purchased	(636,859)	(335,361)
Investments sold	444,637	131,605
Investments called or matured	102,244	103,193
Net change in short-term investments	(8,546)	(6,910)
Net property and equipment purchased	(4,838)	(7,262)
Proceeds from (used in) other investing activities	89	408
Net Cash Used in Investing Activities, Total	(103,273)	(114,327)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Cash dividends paid	(28,815)	(27,288)
Proceeds from stock option exercises	3,917	4,290
Net Cash Used in Financing Activities, Total	(24,898)	(22,998)
Net increase in cash	35,198	8,608
Cash at the beginning of the period	24,271	18,269
Cash at the end of the period	$ 59,469	$ 26,877

Cash inflow (outflow) from stock option exercises.

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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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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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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 cash outflow or inflow from purchases, sales and disposals of property, plant and equipment and other productive assets, including intangibles.

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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 for purchase of marketable security.

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The cash inflow from maturities, prepayments, calls and collections of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, beyond the current operating cycle.

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The cash inflow from sales of all investments, including securities and other assets, having ready marketability and intended by management to be liquidated, if necessary, beyond the current operating cycle.

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