Stockholders' Equity

Share-based Compensation Plans

We maintain two share-based employee compensation plans: the 2012 Equity Incentive Plan (2012 Plan) and the 2005 Stock Plan (collectively, Stock Plans). Our 2012 Plan serves as the successor to our 2005 Stock Plan and provides for the issuance of incentive and nonstatutory stock options, restricted stock awards, stock appreciation rights, RSUs, performance shares and stock bonuses to qualified employees, directors and consultants. Outstanding awards under the 2005 Stock Plan continue to be subject to the terms and conditions of the 2005 Stock Plan. The maximum term for stock options granted under the 2012 Plan may not exceed ten years from the date of grant. Our 2012 Plan will terminate ten years from the date of approval unless it is terminated earlier by our compensation committee.

We have initially reserved 25,000,000 shares of our Class A common stock for issuance under our 2012 Plan, which amount increases on the first day of January of each year through 2022 based on a formula or as determined by the board of directors. Our board of directors elected not to increase the number of shares reserved for issuance in 2014. In addition, shares available for grant under the 2005 Stock Plan, which were reserved but not issued or subject to outstanding awards under the 2005 Stock Plan as of the effective date of our IPO, were added to the reserves of the 2012 Plan and shares that were withheld in connection with the net settlement of RSUs were also added to the reserves of the 2012 Plan. In January 2014, we began requiring that employees sell a portion of the shares that they receive upon the vesting of RSUs in order to cover any required withholding taxes, rather than our previous approach of net share settlement.

In February 2014, we terminated our 2005 Officers' Plan as the only outstanding option issued under this plan had been exercised in full.

The following table summarizes the stock option activity under the Stock Plans during the three months ended March 31, 2014:



	Shares Subject to Options Outstanding
	Number of Shares		Weighted Average Exercise Price		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value⁽¹⁾
	(in thousands)				(in years)	(in millions)
Balance as of December 31, 2013	22,102		$	3.56
Stock options exercised	(2,705	)	0.32
Balance as of March 31, 2014	19,397		$	4.01	4.60	$	1,091
Stock options vested and expected to vest as of March 31, 2014	19,378		$	4.01	4.60	$	1,090
Stock options exercisable as of March 31, 2014	14,911		$	2.06	4.10	$	868


(1)	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock option awards and the closing price of our Class A common stock of $60.24 on March 31, 2014.

The aggregate intrinsic value of the options exercised was $161 million and $311 million for the three months ended March 31, 2014 and 2013, respectively.

The following table summarizes the activities for our unvested RSUs for the three months ended March 31, 2014:



	Unvested RSUs
	Number of Shares		Weighted Average Grant Date Fair Value
	(in thousands)
Unvested at December 31, 2013	103,971		$	27.30
Granted	19,523		68.13
Vested	(14,550	)	24.53
Forfeited	(2,575	)	31.55
Unvested at March 31, 2014	106,369		$	35.07

The fair value as of the respective vesting dates of RSUs that vested during the three months ended March 31, 2014 and 2013 was $952 million and $485 million, respectively.

As of March 31, 2014, there was $3.67 billion of unrecognized share-based compensation expense, of which $3.42 billion is related to RSUs and $254 million is related to restricted shares and stock options. This unrecognized compensation expense is expected to be recognized over a weighted-average period of approximately three years.