Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2013

Stockholders' Equity and Stock-based Compensation Disclosure [Abstract]

Summary Of Activity Related To Stock Option Plans

A summary of the activities related to the Company’s stock option plans is as follows:

			Options Outstanding
	Shares Available for Grant		Number of Shares		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Thousands)
Balances as of December 31, 2012	4,049,037		4,572,952		$	71.33
Granted	(541,378	)	541,378		184.71
Exercised			(1,339,571	)	69.84
Balances as of September 30, 2013	3,507,659		3,774,759		88.12		6.37	$	834,555
Vested and exercisable at September 30, 2013			3,774,759		88.12		6.37	$	834,555

Summary Of Assumptions Used To Value Stock Option Grants Using Lattice-Binomial Model

The following table summarizes the assumptions used to value stock option grants using the lattice-binomial model:

	Three Months Ended				Nine Months Ended
	September 30, 2013		September 30, 2012		September 30, 2013		September 30, 2012
Dividend yield	—	%	—	%	—	%	—	%
Expected volatility	51	%	60	%	51% - 54%		60% - 65%
Risk-free interest rate	2.55	%	1.61	%	1.87% - 2.55%		1.61% - 2.01%
Suboptimal exercise factor	2.43 - 3.79		2.27 - 3.64		2.33 - 3.79		2.26 - 3.65