Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 1,971	$ 1,468	$ 3,245	$ 2,652
Cost of sales
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	43	19	67	34
Fulfillment
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	360	320	594	564
Marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	307	190	516	351
Technology and content
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,077	788	1,752	1,419
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 184	$ 151	$ 316	$ 284