Equity Incentive Plans and Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Shares available for grant under stock-based incentive plans

A summary of shares available for grant under the Company’s plans is as follows:



	Shares Available for Grant
Shares available as of December 31, 2015	11,173,545
Stock options granted	(440,000	)
Stock options forfeited	773,912
Stock options expired under former plans	(412,467	)
Nonvested equity stock and stock units granted (1) (2)	(3,336,963	)
Nonvested equity stock and stock units forfeited (1)	636,828
Total available for grant as of June 30, 2016	8,394,855

_________________________________________


(1)	For purposes of determining the number of shares available for grant under the 2015 Plan (and previously the 2006 Plan) against the maximum number of shares authorized, each share of restricted stock granted reduces the number of shares available for grant by 1.5 shares and each share of restricted stock forfeited increases shares available for grant by 1.5 shares.


(2)	Amount includes 300,003 shares that have been reserved for potential future issuance related to certain performance unit awards granted in the first quarter of 2016 and discussed under the section titled "Nonvested Equity Stock and Stock Units" below.

Schedule of stock option activity

The following table summarizes stock option activity under the 1997 Plan, 2006 Plan and 2015 Plan for the six months ended June 30, 2016 and information regarding stock options outstanding, exercisable, and vested and expected to vest as of June 30, 2016.



	Options Outstanding
	Number of Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
	(In thousands, except per share amounts)
Outstanding as of December 31, 2015	8,995,017		$	10.01
Options granted	440,000		$	12.31
Options exercised	(749,058	)	$	7.01
Options forfeited	(773,912	)	$	21.81
Outstanding as of June 30, 2016	7,912,047		$	9.27	5.67	$	31,293
Vested or expected to vest at June 30, 2016	7,679,174		$	9.30	5.61	$	30,418
Options exercisable at June 30, 2016	4,989,516		$	10.05	4.72	$	18,970

Weighted-average assumptions for Stock Option Plans

The following table presents the weighted-average assumptions used to estimate the fair value of stock options granted that contain only service conditions in the periods presented.



	Stock Option Plans
	Six Months Ended
	June 30,
	2016			2015
Stock Option Plans
Expected stock price volatility	36		%	41		%
Risk free interest rate	1.7		%	1.2		%
Expected term (in years)	6.1			6.0
Weighted-average fair value of stock options granted to employees	$	4.66		$	4.59

Schedule of nonvested equity stock and stock units activity

The following table reflects the activity related to nonvested equity stock and stock units for the six months ended June 30, 2016:



Nonvested Equity Stock and Stock Units	Shares		Weighted- Average Grant-Date Fair Value
Nonvested at December 31, 2015	3,008,118		$	11.32
Granted	2,024,640		$	12.34
Vested	(385,984	)	$	10.15
Forfeited	(284,142	)	$	11.59
Nonvested at June 30, 2016	4,362,632		$	11.88

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]



	Employee Stock Purchase Plan
	Six Months Ended
	June 30,
	2016			2015
Employee Stock Purchase Plan
Expected stock price volatility	33		%	34		%
Risk free interest rate	0.41		%	0.05		%
Expected term (in years)	0.5			0.5
Weighted-average fair value of purchase rights granted under the purchase plan	$	2.86		$	3.48