Common Stock	6 Months Ended
Jun. 30, 2018
Stockholders' Equity Note [Abstract]
Common Stock	Common Stock As of June 30, 2018 and December 31, 2017, there were 58,173,108 and 58,798,428 shares of our common stock outstanding, respectively. During the three months ended June 30, 2018 and 2017, we issued 72,777 and 76,347 shares of common stock, respectively. During the six months ended June 30, 2018 and 2017, we issued 170,930 and 193,381 shares of common stock, respectively. These shares were issued primarily upon: (a) the satisfaction of required conditions under certain of our share-based compensation plans and (b) the purchase of common stock pursuant to our employee stock purchase plan. On September 26, 2011, our Board of Directors authorized us to repurchase up to $100.0 million of our outstanding common stock. On December 5, 2013, October 23, 2014, October 28, 2015 and October 25, 2017, our Board of Directors authorized us to repurchase up to an additional $100.0 million, $250.0 million, $200.0 million and $100.0 million of our outstanding common stock, respectively. During 2018, we have repurchased 796,250 shares of our common stock for approximately $60.5 million. Since the inception of the repurchase programs through June 30, 2018, we have repurchased approximately 13.6 million shares of our common stock for approximately $635.8 million. As of June 30, 2018, there remained authorization for us to repurchase approximately $114.2 million of our shares. The repurchase programs have no expiration date and do not obligate the Company to acquire any particular amount of common stock and may be suspended, recommenced or discontinued at any time or from time to time without prior notice. We may repurchase our shares from time to time to the extent permitted by securities laws and other legal requirements, including provisions in our 2016 Credit Agreement placing limitations on such repurchases. The repurchase programs have been and will be funded from our operations.

Common Stock

As of June 30, 2018 and December 31, 2017, there were 58,173,108 and 58,798,428 shares of our common stock outstanding, respectively.

During the three months ended June 30, 2018 and 2017, we issued 72,777 and 76,347 shares of common stock, respectively. During the six months ended June 30, 2018 and 2017, we issued 170,930 and 193,381 shares of common stock, respectively. These shares were issued primarily upon: (a) the satisfaction of required conditions under certain of our share-based compensation plans and (b) the purchase of common stock pursuant to our employee stock purchase plan.

On September 26, 2011, our Board of Directors authorized us to repurchase up to $100.0 million of our outstanding common stock. On December 5, 2013, October 23, 2014, October 28, 2015 and October 25, 2017, our Board of Directors authorized us to repurchase up to an additional $100.0 million, $250.0 million, $200.0 million and $100.0 million of our outstanding common stock, respectively. During 2018, we have repurchased 796,250 shares of our common stock for approximately $60.5 million. Since the inception of the repurchase programs through June 30, 2018, we have repurchased approximately 13.6 million shares of our common stock for approximately $635.8 million. As of June 30, 2018, there remained authorization for us to repurchase approximately $114.2 million of our shares. The repurchase programs have no expiration date and do not obligate the Company to acquire any particular amount of common stock and may be suspended, recommenced or discontinued at any time or from time to time without prior notice. We may repurchase our shares from time to time to the extent permitted by securities laws and other legal requirements, including provisions in our 2016 Credit Agreement placing limitations on such repurchases. The repurchase programs have been and will be funded from our operations.