Capital Stock	12 Months Ended
Dec. 31, 2018
Stockholders' Equity Note [Abstract]
Capital Stock	CAPITAL STOCK CAPITAL STOCK On June 11, 2018, our stockholders approved an increase in the number of authorized shares of our common stock from 200,000,000 to 400,000,000. Accordingly, on June 11, 2018 we amended our Amended and Restated Certificate of Incorporation to increase the total number of shares of capital which we have authority to issue to 410,000,000 shares, consisting of 400,000,000 shares of common stock, par value $0.01 per share, and 10,000,000 shares of preferred stock, par value of $0.01 per share. TREASURY STOCK On October 17, 2016, our Board of Directors authorized the repurchase by us of up to $300.0 million of our common stock by various means from time to time through and including December 31, 2021. Pursuant to this authorization, we repurchased a total of 188,300 shares of our common stock in 2018 at an average price per share of $25.31, for a total purchase price of $4.8 million. In 2016, pursuant to this authorization and the remaining amount from a prior authorization, we repurchased a total of 294,930 shares of our common stock at an average price per share of $24.40, for a total purchase price of $7.2 million, and we completed a “modified Dutch auction” tender offer pursuant to which we purchased 10,617,810 shares of our common stock from our stockholders at a price of $25.38 per share, for a total purchase price of $269.4 million, exclusive of $0.7 million of fees and expenses. Certain of our directors and executive officers as well as related family foundations participated in the 2016 "modified Dutch auction" tender offer, and we purchased a total of 3,358,572 shares of our common stock beneficially owned by them at a price of $25.38 per share, for a total purchase price of $85.2 million, in such tender offer. Accordingly, at December 31, 2018, we had approximately $124.6 million remaining for the repurchase of our common stock under the October 17, 2016 Board of Directors authorization. In 2018, 2017 and 2016, we issued 339,972 treasury shares, 421,108 treasury shares and 363,368 treasury shares, respectively, at an average cost of $3.12 per share in 2018 and $3.15 per share in each of 2017 and 2016, for restricted stock units that vested during these years. In 2018, 2017 and 2016, we repurchased 107,420 shares, 138,080 shares and 134,122 shares of our common stock, respectively, at an average cost of $28.46, $30.24 and $25.58 per share, respectively, in accordance with the Plan to satisfy employee withholding tax requirements resulting from certain restricted stock units becoming vested. We account for treasury shares using the FIFO cost method. As of December 31, 2018, 64,682,900 shares of our common stock were held in treasury.

CAPITAL STOCK

On June 11, 2018, our stockholders approved an increase in the number of authorized shares of our common stock from 200,000,000 to 400,000,000. Accordingly, on June 11, 2018 we amended our Amended and Restated Certificate of Incorporation to increase the total number of shares of capital which we have authority to issue to 410,000,000 shares, consisting of 400,000,000 shares of common stock, par value $0.01 per share, and 10,000,000 shares of preferred stock, par value of $0.01 per share.

TREASURY STOCK

On October 17, 2016, our Board of Directors authorized the repurchase by us of up to $300.0 million of our common stock by various means from time to time through and including December 31, 2021. Pursuant to this authorization, we repurchased a total of 188,300 shares of our common stock in 2018 at an average price per share of $25.31, for a total purchase price of $4.8 million. In 2016, pursuant to this authorization and the remaining amount from a prior authorization, we repurchased a total of 294,930 shares of our common stock at an average price per share of $24.40, for a total purchase price of $7.2 million, and we completed a “modified Dutch auction” tender offer pursuant to which we purchased 10,617,810 shares of our common stock from our stockholders at a price of $25.38 per share, for a total purchase price of $269.4 million, exclusive of $0.7 million of fees and expenses. Certain of our directors and executive officers as well as related family foundations participated in the 2016 "modified Dutch auction" tender offer, and we purchased a total of 3,358,572 shares of our common stock beneficially owned by them at a price of $25.38 per share, for a total purchase price of $85.2 million, in such tender offer. Accordingly, at December 31, 2018, we had approximately $124.6 million remaining for the repurchase of our common stock under the October 17, 2016 Board of Directors authorization.

In 2018, 2017 and 2016, we issued 339,972 treasury shares, 421,108 treasury shares and 363,368 treasury shares, respectively, at an average cost of $3.12 per share in 2018 and $3.15 per share in each of 2017 and 2016, for restricted stock units that vested during these years. In 2018, 2017 and 2016, we repurchased 107,420 shares, 138,080 shares and 134,122 shares of our common stock, respectively, at an average cost of $28.46, $30.24 and $25.58 per share, respectively, in accordance with the Plan to satisfy employee withholding tax requirements resulting from certain restricted stock units becoming vested.

We account for treasury shares using the FIFO cost method. As of December 31, 2018, 64,682,900 shares of our common stock were held in treasury.