Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity

Stockholders' Equity
9 Months Ended
Sep. 30, 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 480,250  $ 90.08  104,306  $ 89.58 
Options exercised/RSUs vested (113,107) $ 23.91  (50,053) $ 122.16 
Forfeited (10,200) $ 72.01  —  $ — 
Balance as of September 30, 2020 2,313,322  $ 82.79  201,512  $ 107.45 

As of September 30, 2020, outstanding options to purchase 1.6 million shares were exercisable with a weighted average exercise price per share of $72.60.

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 September 30, 2020, 56,079 shares were available for future purchases under the ESPP.

Share Repurchases

During the first quarter of 2020, we repurchased $73.3 million of our common stock under our stock repurchase programs as discussed below. We did not have any share repurchases during the second and third quarter of 2020.

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 may enter into Rule 10b5-1 trading plans, 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. Authorization to repurchase $253.5 million of our common stock remained available as of September 30, 2020.