Description of Business and Accounting Policies - Property and Equipment, Net (Details)	12 Months Ended
	Dec. 31, 2018
Building
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	40 years
Servers
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Networking Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	5 years
Heavy Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	10 years
Minimum | Other Fulfillment Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	3 years
Maximum | Other Fulfillment Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of assets	7 years