Stockholders' Equity - Stock Option Activity (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Employee Stock Options
Number of Shares
Beginning balance	22,102
Stock options exercised	(2,705)
Ending balance	19,397
Stock options vested and expected to vest as of period end	19,378
Stock options exercisable as of period end	14,911
Weighted Average Exercise Price
Beginning Balance (in dollars per share)	$ 3.56
Stock options exercised (in dollars per share)	$ 0.32
Ending Balance (in dollars per share)	$ 4.01
Stock options vested and expected to vest as of period end (in dollars per share)	$ 4.01
Stock options exercisable as of period end (in dollars per share)	$ 2.06
Weighted- Average Remaining Contractual Term
Beginning balance	4 years 7 months 7 days
Stock options vested and expected to vest as of period end	4 years 7 months 7 days
Stock options exercisable as of period end	4 years 1 month 5 days
Aggregate Intrinsic Value
Beginning balance	$ 1,091	[1]
Stock options vested and expected to vest as of period end	1,090	[1]
Stock options exercisable as of period end	$ 868	[1]
Class A Common Stock
Aggregate Intrinsic Value
Common stock, closing share price	$ 60.24

[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.