Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity

Stockholders' Equity
3 Months Ended
Mar. 31, 2020
Equity [Abstract]  
Stockholders' Equity Stockholders’ Equity
We grant options and awards to employees and non-employee directors pursuant to a stockholder approved stock incentive plan, which is described in further detail in Note 9, Stockholders’ Equity, of Notes to Consolidated Financial Statements in our 2019 Annual Report.

The following is a summary of our stock option and restricted stock activity and related information:
Stock Options Restricted Stock Awards
Shares Weighted-Average Exercise Price Shares Weighted-Average Grant Date Fair Value
Balance as of December 31, 2019 1,956,379    $ 77.54    147,259    $ 125.11   
Granted 309,456    $ 95.61    94,508    $ 87.25   
Options exercised/RSUs vested (81,301)   $ 11.70    (43,904)   $ 123.28   
Forfeited —    $ —    —    $ —   
Balance as of March 31, 2020 2,184,534    $ 82.55    197,863    $ 107.43   

As of March 31, 2020, outstanding options to purchase 1.4 million shares were exercisable with a weighted average exercise price per share of $66.97.

Employee Stock Purchase Plan

The price at which common stock is purchased under the Amended Employee Stock Purchase Plan, or ESPP, is equal to 85% of the fair market value of the common stock on the first or last day of the offering period, whichever is lower. As of March 31, 2020, 59,263 shares were available for future purchases under the ESPP.

Share Repurchases

During the three months ended March 31, 2020, we repurchased $73.3 million, of our common stock under our stock repurchase programs as discussed below.
In September 2018, our Board of Directors authorized us to repurchase up to $200.0 million of our common stock from time to time over a period of up to three years. On January 23, 2019, our Board of Directors increased the share repurchase authorization by $150.0 million. The available amount under the $350.0 million repurchase program was fully utilized during the third quarter of 2019.On September 11, 2019, our Board of Directors approved a stock repurchase program authorizing, but not obligating, the repurchase of up to $500.0 million of our common stock from time to time over the next three years. We expect to acquire shares primarily through open-market transactions and have entered into a Rule 10b5-1 trading plan, and may enter into additional Rule 10b5-1 trading plans in the future, to facilitate open-market repurchases. The timing and amount of repurchase transactions will be determined by management based on our evaluation of market conditions, share price, legal requirements and other factors. Our prior $350.0 million stock repurchase program mentioned above was terminated in connection with the approval of the new stock repurchase program. Authorization to repurchase $253.5 million of our common stock remained available as of March 31, 2020.