Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2014

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, 2013	3,406,317		3,526,898		$	95.25
Granted	(391,239	)	391,239		409.70
Exercised			(639,378	)	88.82
Balances as of September 30, 2014	3,015,078		3,278,759		134.02		5.97	$	1,041,797
Vested and exercisable at September 30, 2014			3,278,759		134.02		5.97	$	1,041,797

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, 2014		September 30, 2013		September 30, 2014		September 30, 2013
Dividend yield	—	%	—	%	—	%	—	%
Expected volatility	43	%	51	%	43% - 48%		51% - 54%
Risk-free interest rate	2.52	%	2.55	%	2.52% - 2.83%		1.87% - 2.55%
Suboptimal exercise factor	2.68 - 4.57		2.43 - 3.79		2.66 - 4.57		2.33 - 3.79