Stockholders' Equity (Unvested Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Unvested restricted stock units - number of shares
Unvested as of December 31, 2014 (in shares) | shares	24,619,549
Granted (in shares) | shares	13,116,639
Vested (in shares) | shares	(8,322,365)
Forfeited/canceled (in shares) | shares	(1,757,674)
Unvested as of September 30, 2015 (in shares) | shares	27,656,149
Expected to vest after September 30, 2015 (in shares) | shares	24,359,536
Unvested restricted stock units - weighted-average grant-date fair value
Unvested as of December 31, 2014 (in dollars per share)	$ 487.80
Granted (in dollars per share)	530.39
Vested (in dollars per share)	443.27
Forfeited/canceled (in dollars per share)	487.20
Unvested as of September 30, 2015 (in dollars per share)	520.97
Expected to vest after September 30, 2015 (in dollars per share)	$ 520.97