Treasury Stock	3 Months Ended
Mar. 31, 2019
Equity [Abstract]
Treasury Stock	(7) Treasury Stock The Board of Directors previously authorized the Company’s repurchase of up to an aggregate of $800.0 million of its class A common stock from time to time on the open market through April 29, 2023 (the “Share Repurchase Program”), although the program may be suspended or discontinued by the Company at any time. The timing and amount of any shares repurchased will be determined by the Company’s management based on its evaluation of market conditions and other factors. The Share Repurchase Program may be funded using the Company’s working capital, as well as proceeds from any other funding arrangements that the Company may enter into in the future. During the three months ended March 31, 2019, the Company repurchased an aggregate of 362,148 shares of its class A common stock at an average price per share of $133.21 and an aggregate cost of $48.2 million pursuant to the Share Repurchase Program. As of March 31, 2019, the Company had repurchased an aggregate of 5,069,762 shares of its class A common stock at an average price per share of $99.51 and an aggregate cost of $504.5 million pursuant to the Share Repurchase Program. The average price per share and aggregate cost amounts disclosed above include broker commissions. During the three months ended March 31, 2018, the Company did not repurchase any shares of its class A common stock pursuant to the Share Repurchase Program.

Treasury Stock

3 Months Ended

Mar. 31, 2019

(7) Treasury Stock

The Board of Directors previously authorized the Company’s repurchase of up to an aggregate of $800.0 million of its class A common stock from time to time on the open market through April 29, 2023 (the “Share Repurchase Program”), although the program may be suspended or discontinued by the Company at any time. The timing and amount of any shares repurchased will be determined by the Company’s management based on its evaluation of market conditions and other factors. The Share Repurchase Program may be funded using the Company’s working capital, as well as proceeds from any other funding arrangements that the Company may enter into in the future. During the three months ended March 31, 2019, the Company repurchased an aggregate of 362,148 shares of its class A common stock at an average price per share of $133.21 and an aggregate cost of $48.2 million pursuant to the Share Repurchase Program. As of March 31, 2019, the Company had repurchased an aggregate of 5,069,762 shares of its class A common stock at an average price per share of $99.51 and an aggregate cost of $504.5 million pursuant to the Share Repurchase Program. The average price per share and aggregate cost amounts disclosed above include broker commissions. During the three months ended March 31, 2018, the Company did not repurchase any shares of its class A common stock pursuant to the Share Repurchase Program.