Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2015

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, as adjusted for the Stock Split, 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, 2014	20,025,208		22,845,417		$	21.65
Granted	(1,916,299	)	1,916,299		66.07
Exercised			(3,093,944	)	11.01
Balances as of June 30, 2015	18,108,909		21,667,772		$	27.09	6.40	$	1,446,423
Vested and exercisable as of June 30, 2015			21,667,772		$	27.09	6.40	$	1,446,423

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 and the valuation data, as adjusted for the Stock Split:



	Three Months Ended						Six Months Ended
	June 30, 2015			June 30, 2014			June 30, 2015			June 30, 2014
Dividend yield	—		%	—		%	—		%	—		%
Expected volatility	36		%	45		%	36		%	45% - 48%
Risk-free interest rate	2.05		%	2.66		%	2.03% - 2.05%			2.66% - 2.83%
Suboptimal exercise factor	2.47			2.66 - 4.20			2.47 -2.48			2.66 - 4.20
Valuation data:
Weighted-average fair value (per share)	$	32.52		$	28.13		$	29.24		$	29.69
Total stock-based compensation expense (in thousands)	$	28,590		$	29,285		$	56,031		$	55,110
Total income tax benefit related to stock options (in thousands)	$	10,796		$	11,225		$	21,188		$	21,124