Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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

Schedule of Stock Based Compensation Expense

The following table summarizes the components of total stock-based compensation expense included in the Company’s consolidated statements of income for the years ended December 31, 2018, 2017 and 2016 (in thousands):

	2018			2017			2016
Cost of revenue	$	21,892		$	20,314		$	18,287
Research and development	44,034			38,864			29,739
Sales and marketing	64,373			60,246			55,407
General and administrative	53,514			44,884			41,073
Total stock-based compensation	183,813			164,308			144,506
Provision for income taxes	(48,502		)	(56,237		)	(49,014		)
Total stock-based compensation, net of taxes	$	135,311		$	108,071		$	95,492

Schedule of Assumptions Used

The grant-date fair values of awards granted under the 1999 ESPP during the years ended December 31, 2018, 2017 and 2016 were estimated using the Black-Scholes option pricing model with the following weighted-average assumptions:

	2018		2017		2016
Expected term (in years)	0.5		0.5		0.5
Risk-free interest rate	1.9	%	1.0	%	0.5	%
Expected volatility	31.2	%	35.8	%	36.2	%
Dividend yield	—	%	—	%	—	%

The grant-date fair values of the Company's RSUs with market-based vesting conditions granted during the year ended December 31, 2018, 2017 and 2016 were estimated using a Monte Carlo simulation model with the following assumptions:

	2018		2017		2016
Expected term (in years)	3.0		3.0		3.0
Risk-free interest rate	2.3	%	1.4	%	0.8	%
Akamai historical share price volatility	35.5	%	33.2	%	34.3	%
Average volatility of peer-company share price	26.3	%	27.1	%	27.6	%

Schedule of Summary of Stock Option Activity

The following table summarizes stock option activity during the year ended December 31, 2018:

	Shares (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2018	339		$	36.36
Exercised	(219	)	35.83
Outstanding at December 31, 2018	120		$	37.33	1.78	$	2,852
Exercisable at December 31, 2018	120		$	37.33	1.78	$	2,852
Vested or expected to vest December 31, 2018	120		$	37.33	1.78	$	2,852

Schedule Of Deferred Stock Units Activity

The following table summarizes the DSU activity for the year ended December 31, 2018:

	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2018	177		$	43.77
Granted	34		76.00
Vested and distributed	(40	)	46.25
Outstanding at December 31, 2018	171		$	49.54

Schedule of Restricted Stock Units by Type

The following table summarizes the different types of restricted stock units ("RSUs") granted by the Company during the year ended December 31, 2018 (in thousands):

	December 31, 2018
RSUs with service-based vesting conditions	3,122
RSUs with market-based vesting conditions	115
RSUs with performance-based vesting conditions	251
Total	3,488

Schedule of Restricted Stock Units Activity

The following table summarizes the RSU activity for the year ended December 31, 2018:

	Units (in thousands)		Weighted Average Grant Date Fair Value
Outstanding at January 1, 2018	5,843		$	59.94
Granted	3,488		69.14
Vested	(2,954	)	60.18
Forfeited	(765	)	61.27
Outstanding at December 31, 2018	5,612		$	62.25