Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 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	(116,439	)	116,439		407.31
Exercised			(333,335	)	97.34
Balances as of March 31, 2014	3,289,878		3,310,002		106.01		5.98	$	821,101
Vested and exercisable at March 31, 2014			3,310,002		106.01		5.98	$	821,101

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
	March 31, 2014		March 31, 2013
Dividend yield	—	%	—	%
Expected volatility	48	%	54	%
Risk-free interest rate	2.83	%	1.87	%
Suboptimal exercise factor	2.66 - 4.07		2.33 - 3.59