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Equity Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

Equity Compensation Plans [Abstract]

Activity Under Stock Based Compensation Plans

Activity under the plans during 2017 was as follows:




									Weighted
						Weighted			Average
			Number of			Average			Remaining			Aggregate
			Shares			Exercise			Contractual			Intrinsic
Time-Based Stock Options			Outstanding			Price			Term			Value
Outstanding at January 1, 2017			2,454		$	12.51
Granted			65			20.22
Exercised			(458)			9.61
Cancelled			(35)			19.08
Outstanding at December 31, 2017			2,026		$	13.30			5.62		$	11,730
Vested and expected to vest			2,004		$	13.23			5.58		$	11,717
Exercisable at December 31, 2017			1,766		$	12.48			5.20		$	11,471


						Weighted
			Number of			Average
			Shares			Grant Date
Restricted Stock			Outstanding			Fair Value
Outstanding at January 1, 2017			1,416		$	17.40
Awarded			771			19.38
Released			(331)			17.43
Forfeited			(11)			18.52
Outstanding at December 31, 2017			1,845		$	18.22


									Weighted
						Weighted			Average
			Number of			Average			Remaining			Aggregate
			Shares			Exercise			Contractual			Intrinsic
Performance Stock Options			Outstanding			Price			Term			Value
Outstanding at January 1, 2017			450		$	13.48
Granted			—			—
Exercised			—			—
Cancelled			—			—
Outstanding at December 31, 2017			450		$	13.48			5.45		$	2,774
Exercisable at December 31, 2017			250		$	13.48			5.45		$	1,541





Activity under the plans during 2016 was as follows:







									Weighted
						Weighted			Average
			Number of			Average			Remaining			Aggregate
			Shares			Exercise			Contractual			Intrinsic
Time-Based Stock Options			Outstanding			Price			Term			Value
Outstanding at January 1, 2016			2,734		$	11.75
Granted			215			16.74
Exercised			(394)			8.47
Cancelled			(101)			16.66
Outstanding at December 31, 2016			2,454		$	12.51			6.02		$	18,295
Vested and expected to vest			2,420		$	12.42			5.99		$	18,228
Exercisable at December 31, 2016			1,914		$	11.01			5.40		$	16,897


						Weighted
			Number of			Average
			Shares			Grant Date
Restricted Stock			Outstanding			Fair Value
Outstanding at January 1, 2016			1,071		$	17.30
Awarded			710			16.35
Forfeited			(70)			17.31
Released			(295)			14.49
Outstanding at December 31, 2016			1,416		$	17.40


									Weighted
						Weighted			Average
			Number of			Average			Remaining			Aggregate
			Shares			Exercise			Contractual			Intrinsic
Performance Stock Options			Outstanding			Price			Term			Value
Outstanding at January 1, 2016			450		$	13.48
Granted			—			—
Exercised			—			—
Cancelled			—			—
Outstanding at December 31, 2016			450		$	13.48			6.45		$	3,074
Exercisable at December 31, 2016			250		$	13.48			6.45		$	1,708



Share-Based Compensation Expense Related to Employee Share-Based Compensation



		2017			2016			2015
Cost of revenue		$	610		$	420		$	416
Research and development expenses			2,052			1,825			1,373
Selling, general and administrative expenses			11,953			9,452			7,208
Total		$	14,615		$	11,697		$	8,997



Assumptions Used for Determining Fair Value of Options



			2017				2016				2015
Risk-free interest rate			1.75 - 2.12	%			1.06 - 2.02	%			1.30 - 1.96	%
Expected life of option (years)			5.21 to 5.76				5.27 to 7.10				5.20 to 6.89
Expected volatility of stock			43.00 - 48.00	%			46.00 - 51.00	%			46.00 - 67.00	%
Weighted-average volatility			44.50	%			48.87	%			54.75	%
Dividend yield			0.00	%			0.00	%			0.00	%



Weighted Average Estimated Grant Date Fair Value Per Share of Stock Options and Restricted Stock Granted



		2017				2016				2015
Stock options		$	8.60			$	8.25			$	11.12
Restricted stock			19.38				16.35				17.82



Estimated Grant Date Fair Value Per Share of Performance Options Granted



		Price				Fair Value of				Fair Value of
		Target				2012 Grant				2014 Grant
Tranche 1		$	10.00			$	4.32			$	14.74
Tranche 2			12.50				4.30				14.74
Tranche 3			15.00				4.27				14.74
Tranche 4			17.50				4.23				14.74
Tranche 5			20.00				4.19				14.73
Tranche 6			25.00				4.10				14.73
Tranche 7			30.00				4.01				14.71
Tranche 8			35.00				3.92				14.67
Tranche 9			40.00				3.83				14.61



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Share based compensation arrangement performance options grants in period estimated grant date fair value.

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Tabular disclosure of the allocation of equity-based compensation costs to a given line item on the balance sheet and income statement for the period. This may include the reporting line for the costs and the amount capitalized and expensed.

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Tabular disclosure for share-based compensation plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value.

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Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.

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Tabular disclosure of the weighted-average grant-date fair value of equity options or other equity instruments granted during the year.

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