Stockholders' Equity - Stock Option Activity (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Employee Stock Options
Number of Shares
Beginning balance (in shares)	22,102
Stock options exercised (in shares)	(5,015)
Ending balance (in shares)	17,087
Stock options vested and expected to vest as of period end (in shares)	17,071
Stock options exercisable as of period end (in shares)	13,719
Weighted Average Exercise Price
Beginning Balance (in dollars per share)	$ 3.56
Stock options exercised (in dollars per share)	$ 0.91
Ending Balance (in dollars per share)	$ 4.34
Stock options vested and expected to vest as of period end (in dollars per share)	$ 4.33
Stock options exercisable as of period end (in dollars per share)	$ 2.48
Weighted- Average Remaining Contractual Term
Balance at period end (in years)	3 years 2 months 20 days
Stock options vested and expected to vest as of period end (in years)	3 years 2 months 20 days
Stock options exercisable as of period end (in years)	2 years 6 months 22 days
Aggregate Intrinsic Value
Balance at period end	$ 1,276	[1]
Stock options vested and expected to vest as of period end	1,275	[1]
Stock options exercisable as of period end	$ 1,050	[1]
Class A Common Stock
Aggregate Intrinsic Value
Common stock, closing share price (in usd per share)	$ 79.04

[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 $79.04 on September 30, 2014.