Authorized shares of common and preferred stock and stock-based compensation plans	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Authorized shares of common and preferred stock and stock-based compensation plans	Authorized shares of common and preferred stock and stock-based compensation plans Authorized shares of common and preferred stock Following approval by the Company’s Board of Directors and stockholders, on May 14, 2013, the Company’s certificate of incorporation was amended to increase the authorized shares of common stock by 180,000,000 shares to a total of 360,000,000 shares. As a result of this amendment, the total number of shares which the Company is authorized to issue is 365,000,000 shares, consisting of (i) 5,000,000 shares of preferred stock, par value $0.01 per share, and (ii) 360,000,000 shares of common stock, par value $0.01 per share. Restricted stock unit plans Our stockholders approved our 2005 Incentive Plan (the “2005 Plan”) in May 2005. At the time of approval, 4,050,000 shares of our common stock were reserved for issuance under the 2005 Plan, as well as the number of shares which had been reserved but not issued under our 1994 Incentive Plan (the “1994 Plan”) which terminated in May 2005, and any shares that returned to the 1994 Plan as a result of termination of options or repurchase of shares issued under such plan. The 2005 Plan, provided for the granting of incentive awards in the form of restricted stock and RSUs to directors, executive officers and employees of the Company and its subsidiaries. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten-year awards may accelerate based on our previous year’s earnings and growth but ten-year awards cannot accelerate to vest over a period of less than five years. The 2005 Plan terminated on May 11, 2010, except with respect to outstanding awards previously granted thereunder. There were 3,362,304 shares of common stock that were reserved but not issued under the 2005 Plan as of May 11, 2010. Our stockholders approved our 2010 Incentive Plan (the “2010 Plan”) on May 11, 2010. At the time of approval, 3,000,000 shares of our common stock were reserved for issuance under the 2010 Plan, as well as the 3,362,304 shares of common stock that were reserved but not issued under the 1994 Plan and the 2005 Plan as of May 11, 2010, and any shares that are returned to the 1994 Plan and the 2005 Plan as a result of the forfeiture or termination of options or RSUs or repurchase of shares issued under those plans. The 2010 Plan, provided for the granting of incentive awards in the form of restricted stock and RSUs to employees, directors and consultants of the Company and employees and consultants of any parent or subsidiary of the Company. Awards vest over a three, five or ten-year period, beginning on the date of grant. Vesting of ten-year awards may accelerate based on our previous year’s earnings and growth but ten-year awards cannot accelerate to vest over a period of less than five years. The 2010 Plan terminated on May 12, 2015, except with respect to the outstanding awards previously granted thereunder. There were 2,518,416 shares of common stock that were reserved but not issued under the 2010 Plan as of May 12, 2015. Our stockholders approved our 2015 Equity Incentive Plan (the “2015 Plan”) on May 12, 2015. At the time of approval, 3,000,000 shares of our common stock were reserved for issuance under the 2015 Plan, as well as the 2,518,416 shares of common stock that were reserved but not issued under the 2010 Plan as of May 12, 2015, and any shares that were returned to the 1994, 2005, and the 2010 Plans as a result of the forfeiture or termination of options or RSUs or repurchase of shares issued under those plans. The 2015 Plan provides for the granting of incentive awards in the form of restricted stock and RSUs to employees, directors and consultants of the Company and employees and consultants of any parent or subsidiary of the Company and such awards may be subject to performance-based vesting conditions. Awards generally vest over a three, four, five or ten-year period, beginning on the date of grant. Vesting of ten-year awards may accelerate based on our previous year’s earnings and growth but ten-year awards cannot accelerate to vest over a period of less than five years. The 2015 plan terminated on May 5, 2020, except with respect to the outstanding awards previously granted thereunder. There were 567,142 shares of common stock that were reserved but not issued under the 2015 Plan as of May 5, 2020. Our stockholders approved our 2020 Equity Incentive Plan (the "2020 Plan") on May 5, 2020. At the time of approval, 4,500,000 shares of our common stock were reserved for issuance under the 2020 Plan, as well as the 567,142 shares of common stock that were reserved but not issued under the 2015 Plan as of May 5, 2020, and any shares that were returned to the 2005, 2010, and 2015 Plans as a result of the forfeiture or termination of RSUs or repurchase of shares issued under those plans. The 2020 Plan provides for the granting of incentive awards in the form of restricted stock and RSUs to employees, directors and consultants of the Company and employees and consultants of any parent or subsidiary of the Company. Awards generally vest over a one, three or four-year period, beginning on the date of the grant and awards may be subject to performance-based vesting conditions. There were 5,104,408 shares available for grant under the 2020 Plan at June 30, 2020. Employee stock purchase plan Our employee stock purchase plan ("ESPP") permits substantially all domestic employees and employees of designated subsidiaries to acquire our common stock at a purchase price of 85% of the lower of the market price at the beginning or the end of the purchase period. The plan has quarterly purchase periods generally beginning on February 1, May 1, August 1 and November 1 of each year. Employees may designate up to 15% of their compensation for the purchase of common stock under the ESPP. On May 14, 2019, our stockholders approved an additional 3,000,000 shares for issuance under our employee stock purchase plan. At June 30, 2020, we had 3,577,369 shares of common stock reserved for future issuance under the ESPP. We issued 508,401 shares under this plan in the six months ended June 30, 2020 and the weighted average purchase price was $33.93 per share. During the six months ended June 30, 2020, we did not make any changes in accounting principles or methods of estimates with respect to our ESPP. Authorized Preferred Stock and Preferred Stock Purchase Rights Plan We have 5,000,000 authorized shares of preferred stock. On January 21, 2004, our Board of Directors designated 750,000 of these shares as Series A Participating Preferred Stock in conjunction with the adoption of a Preferred Stock Rights Agreement which expired on May 10, 2014. There were no shares of preferred stock issued and outstanding at June 30, 2020. Stock repurchases and retirements From time to time, our Board of Directors has authorized various programs for our repurchase of shares of our common stock depending on market conditions and other factors. Under the current program, during the three months ended June 30, 2020, we repurchased 503,326 shares of our common stock at a weighted average price per share of $34.08 and during the six months ended June 30, 2020, we repurchased 668,199 shares of our common stock at a weighted average price per share of $35.44. Under the current program, during the three months ended June 30, 2019, we repurchased 1,114,500 shares of our common stock at a weighted average price per share of $41.25 and during the six months ended June 30, 2019, we repurchased 2,149,598 shares of our common stock at a weighted average price per share of $42.97. At June 30, 2020, there were 2,331,801 shares remaining available for repurchase under the stock repurchase program. The stock repurchase program does not have an expiration date.