Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2017

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

Stock-Based Compensation Expense

Stock-based compensation expense is as follows (in millions):

	Three Months Ended   September 30,				Nine Months Ended   September 30,
	2016		2017		2016		2017
Cost of sales (1)	$	7	$	13	$	7	$	33
Fulfillment	165		230		467		655
Marketing	85		135		221		363
Technology and content	434		595		1,171		1,668
General and administrative	85		112		222		317
Total stock-based compensation expense	$	776	$	1,085	$	2,088	$	3,036

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(1) Beginning in Q3 2016, stock-based compensation expense was recorded to cost of sales for eligible employees providing delivery services.

Nonvested Restricted Stock Units Activity

The following table summarizes our restricted stock unit activity for the nine months ended September 30, 2017 (in millions):

	Number of Units		Weighted-Average Grant-Date Fair Value
Outstanding as of December 31, 2016	19.8		$	506
Units granted	7.2		918
Units vested	(4.6	)	387
Units forfeited	(1.3	)	620
Outstanding as of September 30, 2017	21.1		$	666

Nonvested Share Activity

Scheduled vesting for outstanding restricted stock units as of September 30, 2017, is as follows (in millions):

	Three Months Ended December 31,	Year Ended December 31,
	2017	2018	2019	2020	2021	Thereafter	Total
Scheduled vesting—restricted stock units	2.2	7.3	7.0	3.1	1.1	0.4	21.1