Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 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:

	Shares Available for Grant		Options Outstanding			Weighted- Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Thousands)
			Number of Shares		Weighted- Average Exercise Price
Balances as of December 31, 2010	2,038,502		2,892,130		36.11
Authorized	5,700,000		—		—
Granted	(724,994	)	724,994		154.09
Exercised	—		(659,370	)	29.11
Balances as of December 31, 2011	7,013,508		2,957,754		66.59
Granted	(1,803,798	)	1,803,798		73.94
Exercised	—		(188,552	)	21.85
Canceled	48		(48	)	35.95
Expired	(1,160,721	)	—
Balances as of December 31, 2012	4,049,037		4,572,952		71.33
Granted	(642,720	)	642,720		208.94
Exercised	—		(1,688,774	)	73.75
Balances as of December 31, 2013	3,406,317		3,526,898
Vested and exercisable at December 31, 2013			3,526,898		95.25	6.16	$	962,570

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

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

	Year Ended December 31,
	2013		2012		2011
Dividend yield	—	%	—	%	—	%
Expected volatility	51% - 54%		55% - 65%		51% – 65%
Risk-free interest rate	1.87% - 2.71%		1.61% - 2.01%		2.05% – 3.42%
Suboptimal exercise factor	2.33 - 3.92		2.26 - 3.65		2.17 – 3.64

Summary Of Stock Repurchases

The following table presents a summary of the Company’s stock repurchases for the year ended December 31, 2011 (in thousands, except per share data):

Total number of shares repurchased	900
Dollar amount of shares repurchased	$	199,666
Average price paid per share	$	221.88
Range of price paid per share	$160.11 – $248.78