Shareholders' Equity	12 Months Ended
Dec. 31, 2018
Equity [Abstract]
Shareholders’ Equity	Shareholders’ Equity Preferred Stock The Company has 400,000 shares of authorized but unissued $.01 par value preferred stock. Common Stock On April 25, 2018, the Company's shareholders approved an amendment to the Company's Articles of Organization to increase the authorized number of shares of common stock from 200,000,000 to 300,000,000. In addition, on April 25, 2018, the Company's shareholders approved an amendment and restatement of the Company's 2001 General Stock Option Plan which provides for an increase in the number of available shares by 10,000,000. In October 2017, the Company’s Board of Directors declared a two-for-one stock split, effected in the form of a stock dividend, on the shares of the Company’s common stock. Each shareholder of record on November 17, 2017 received an additional share of common stock for each share of common stock then held. The stock was distributed on December 1, 2017. The Company retained the current par value of $.002 per share for all shares of common stock. All references in the financial statements to the number of shares outstanding, number of shares repurchased, per-share amounts, and stock option data related to the Company’s common stock have been adjusted to reflect the effect of the stock split for all periods presented. Shareholders’ equity reflects the stock split by reclassifying from “Additional paid in capital” and "Retained earnings" to “Common stock” an amount equal to the par value of the additional shares arising from the split. Each outstanding share of common stock entitles the record holder to one vote on all matters submitted to a vote of the Company’s shareholders. Common shareholders are also entitled to dividends when and if declared by the Company’s Board of Directors. Shareholder Rights Agreement On December 4, 2008, the Company adopted a Shareholder Rights Agreement to provide shareholders with the opportunity to benefit from the long-term prospects and value of the Company and to ensure that shareholders receive fair and equal treatment in the event of any proposed takeover of the Company. The Shareholder Rights Agreement, which was previously filed by the Company with the Securities and Exchange Commission as an exhibit to the Registration Statement on Form 8-A filed on December 5, 2008, could have made it more difficult for a third party to acquire, or could have discouraged a third party from acquiring, the Company or a large block of the Company’s common stock. The Company determined to allow the Shareholder Rights Agreement and associated rights to expire in accordance with their terms on December 5, 2018 without renewal. Stock Repurchases In April 2017, the Company's Board of Directors authorized the repurchase of $100,000,000 of the Company's common stock. The Company repurchased 1,744,000 shares at a cost of $100,000,000 under this program, including 803,000 shares at a cost of $45,200,000 in the first quarter of 2018. In February 2018, the Company's Board of Directors authorized the repurchase of $150,000,000 of the Company's common stock. The Company repurchased 3,174,000 shares at a cost of $150,000,000 under this program. In October 2018, the Company's Board of Directors authorized the repurchase of $200,000,000 of the Company's common stock. As of December 31, 2018, the Company repurchased 203,000 shares at a cost of $8,622,000 under this program, leaving a remaining balance of $191,378,000. Total stock repurchases in 2018 amounted to $203,822,000. The Company may repurchase shares under this program in future periods depending on a variety of factors, including, among other things, the impact of dilution from employee stock options, stock price, share availability, and cash requirements. Dividends The Company’s Board of Directors declared and paid cash dividends of $0.0375 per share in the first quarter of 2017, $0.0425 in the second and third quarters of 2017, and $0.0450 in the fourth quarter of 2017, as well as in the first, second, and third quarters of 2018. The dividend was increased to $0.0500 in the fourth quarter of 2018. Total dividends amounted to $31,865,000 and $29,037,000 in 2018 and 2017, respectively. Future dividends will be declared at the discretion of the Company's Board of Directors and will depend upon such factors as the Board deems relevant, including, among other things, the Company's ability to generate positive cash flow from operations.

Shareholders’ Equity

Preferred Stock

The Company has 400,000 shares of authorized but unissued $.01 par value preferred stock.

Common Stock

On April 25, 2018, the Company's shareholders approved an amendment to the Company's Articles of Organization to increase the authorized number of shares of common stock from 200,000,000 to 300,000,000. In addition, on April 25, 2018, the Company's shareholders approved an amendment and restatement of the Company's 2001 General Stock Option Plan which provides for an increase in the number of available shares by 10,000,000.

In October 2017, the Company’s Board of Directors declared a two-for-one stock split, effected in the form of a stock dividend, on the shares of the Company’s common stock. Each shareholder of record on November 17, 2017 received an additional share of common stock for each share of common stock then held. The stock was distributed on December 1, 2017. The Company retained the current par value of $.002 per share for all shares of common stock. All references in the financial statements to the number of shares outstanding, number of shares repurchased, per-share amounts, and stock option data related to the Company’s common stock have been adjusted to reflect the effect of the stock split for all periods presented. Shareholders’ equity reflects the stock split by reclassifying from “Additional paid in capital” and "Retained earnings" to “Common stock” an amount equal to the par value of the additional shares arising from the split.

Each outstanding share of common stock entitles the record holder to one vote on all matters submitted to a vote of the Company’s shareholders. Common shareholders are also entitled to dividends when and if declared by the Company’s Board of Directors.

Shareholder Rights Agreement

On December 4, 2008, the Company adopted a Shareholder Rights Agreement to provide shareholders with the opportunity to benefit from the long-term prospects and value of the Company and to ensure that shareholders receive fair and equal treatment in the event of any proposed takeover of the Company. The Shareholder Rights Agreement, which was previously filed by the Company with the Securities and Exchange Commission as an exhibit to the Registration Statement on Form 8-A filed on December 5, 2008, could have made it more difficult for a third party to acquire, or could have discouraged a third party from acquiring, the Company or a large block of the Company’s common stock. The Company determined to allow the Shareholder Rights Agreement and associated rights to expire in accordance with their terms on December 5, 2018 without renewal.

Stock Repurchases

In April 2017, the Company's Board of Directors authorized the repurchase of $100,000,000 of the Company's common stock. The Company repurchased 1,744,000 shares at a cost of $100,000,000 under this program, including 803,000 shares at a cost of $45,200,000 in the first quarter of 2018. In February 2018, the Company's Board of Directors authorized the repurchase of $150,000,000 of the Company's common stock. The Company repurchased 3,174,000 shares at a cost of $150,000,000 under this program. In October 2018, the Company's Board of Directors authorized the repurchase of $200,000,000 of the Company's common stock. As of December 31, 2018, the Company repurchased 203,000 shares at a cost of $8,622,000 under this program, leaving a remaining balance of $191,378,000. Total stock repurchases in 2018 amounted to $203,822,000. The Company may repurchase shares under this program in future periods depending on a variety of factors, including, among other things, the impact of dilution from employee stock options, stock price, share availability, and cash requirements.

Dividends

The Company’s Board of Directors declared and paid cash dividends of $0.0375 per share in the first quarter of 2017, $0.0425 in the second and third quarters of 2017, and $0.0450 in the fourth quarter of 2017, as well as in the first, second, and third quarters of 2018. The dividend was increased to $0.0500 in the fourth quarter of 2018. Total dividends amounted to $31,865,000 and $29,037,000 in 2018 and 2017, respectively. Future dividends will be declared at the discretion of the Company's Board of Directors and will depend upon such factors as the Board deems relevant, including, among other things, the Company's ability to generate positive cash flow from operations.