Stockholders' Equity
 3 Months Ended
Mar. 31, 2018
Equity [Abstract]  
Stockholders' Equity
Stockholders' Equity
Common Stock
Our certificate of incorporation, as amended and restated, authorizes us to issue 75,000,000 shares of Class B common stock at $0.0001 par value per share, and 750,000,000 shares of Class A common stock at $0.0001 par value per share. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each holder of Class B common stock is entitled to ten votes per share and each holder of Class A common stock is entitled to one vote per share. Shares of Class B common stock may be converted into Class A common stock at any time at the option of the stockholder and are automatically converted upon sale or transfer to Class A common stock, subject to certain limited exceptions. At its discretion, the board of directors may declare dividends on shares of common stock, subject to the rights of our preferred stockholders, if any. Upon liquidation or dissolution, holders of common stock will receive distributions only after preferred stock preferences have been satisfied.
Preferred Stock
Our certificate of incorporation, as amended and restated, authorizes us to issue 10,000,000 shares of preferred stock at $0.0001 par value per share. Our board of directors has the authority to provide for the issuance of all the shares in one or more series. At its discretion, our board of directors may designate the voting rights and preferences of the preferred stock. As of March 31, 2018 and December 31, 2017, no shares of preferred stock were outstanding.
Stock Repurchase Program
On November 1, 2016, we announced that our board of directors approved a stock repurchase program, under which we were authorized to repurchase up to $200 million of our outstanding Class A common stock. The repurchase program has no expiration date and may be modified, suspended or discontinued at any time. Repurchases under the program may be made from time to time on the open market at prevailing market prices, in privately negotiated transactions, in transactions structured through investment banking institutions or a combination of the foregoing, in compliance with Rule 10b-18 under the Securities Exchange Act of 1934.
During the three months ended March 31, 2018, we repurchased 366,160 shares of our outstanding Class A common stock at an average price of $81.95 per share for $30.0 million. During the three months ended March 31, 2017, we repurchased 383,411 shares of our outstanding Class A common stock at an average price of $52.18 per share for $20.0 million. All repurchases were made in open market transactions using cash on hand, and all of the shares repurchased were retired. As of March 31, 2018, we were authorized to repurchase a remaining $70.0 million of our Class A common stock under our repurchase program.
On April 26, 2018, our board of directors authorized us to repurchase up to an additional $300 million of our Class A common stock under our previously announced stock repurchase program. Including the additional $300 million, we are authorized to repurchase up to a remaining $370.0 million of our Class A common stock under the existing stock repurchase program. As of March 31, 2018, we had repurchased and retired 2,077,105 shares of our Class A common stock, under the existing stock repurchase program, for a total purchase price of $130.0 million.