Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2012

Stockholders' Equity Note [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, 2009	2,591,267		4,241,438		$	22.74
Granted	(552,765	)	552,765		99.58
Exercised	—		(1,902,073	)	24.75
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		7.05	$	163,975
Vested and exercisable at December 31, 2012			4,572,952		71.33		7.05	$	163,975

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,
	2012		2011		2010
Dividend yield	—	%	—	%	—	%
Expected volatility	55 % - 65%		51% – 65%		46% – 54%
Risk-free interest rate	1.61% - 2.01%		2.05% – 3.42%		2.65% – 3.67%
Suboptimal exercise factor	2.26 - 3.65		2.17 – 3.64		1.78 – 3.28

Summary Of Stock Repurchases

The following table presents a summary of the Company’s stock repurchases:

	Year ended December 31,
	2011		2010
	(in thousands, except per share data)
Total number of shares repurchased	900		2,606
Dollar amount of shares repurchased	$	199,666	$	210,259
Average price paid per share	$	221.88	$	80.67
Range of price paid per share	$160.11 – $248.78		$60.23 – $126.01