v3.8.0.1

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Stock options

Stock-Based Compensation

Schedule of stock-based compensation expense included in the consolidated statements of operations and comprehensive loss

		Year Ended December 31,
		2017			2016			2015
		(in thousands)
Curriculum and teaching		$	3		$	—		$	—
Servicing and support			4,036			3,245			2,270
Technology and content development			3,306			2,392			1,548
Marketing and sales			1,742			1,317			1,057
General and administrative			12,843			8,869			7,624
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Total stock-based compensation expense		$	21,930		$	15,823		$	12,499
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Summary assumptions used for estimating the fair value of the stock options granted

		Year Ended December 31,
		2017		2016		2015
Risk-free interest rate		2.0% - 2.1%		1.1% - 1.9%		1.5% - 1.9%
Expected term (years)		6.00 - 6.08		5.43 - 6.50		5.56 - 6.08
Expected volatility		46% - 49%		50%		50%
Dividend yield		0%		0%		0%

Summary of stock option activity

Number of Options

Weighted-Average Exercise Price per Share

Weighted-Average Remaining Contractual Term (in years)

Aggregate Intrinsic Value (in thousands)

Outstanding balance at December 31, 2016

4,882,237

$

10.74

6.30

$

95,081

Granted

605,640

40.90

8.95

Exercised

(846,821

)

7.81

3.97

Forfeited

(65,853

)

23.63

Expired

(16,027

)

13.26

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Outstanding balance at December 31, 2017

4,559,176

15.10

5.88

225,283

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Exercisable at December 31, 2017

3,357,682

8.96

4.92

186,529

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Vested and expected to vest at December 31, 2017

4,559,176

15.10

5.88

225,283

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Restricted Stock Units

Stock-Based Compensation

Summary of restricted stock unit activity

		Number of Restricted Stock Units			Weighted-Average Grant Date Fair Value per Share
Outstanding balance at December 31, 2016			1,412,934		$	20.60
Granted			620,259			41.74
Vested			(494,504	)		18.98
Forfeited			(125,266	)		26.16
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Outstanding balance at December 31, 2017			1,413,423			29.95
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X

- Definition

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.

+ References

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- Definition

Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year.

+ References

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- Definition

Tabular disclosure for stock option 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.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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