Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 30, 2020	Feb. 29, 2020	Dec. 31, 2019
Property and equipment, net
Computer equipment	$ 11,453				$ 11,453
Capitalized software	19,072				18,516
Fulfillment equipment	49,600				54,059
Furniture and fixtures	3,513				3,725
Leasehold improvements	32,254				41,735
Buildings	114,877				148,507
Construction in process	2,034				1,803
Property and equipment, gross	232,803				279,798
Less: accumulated depreciation and amortization	(94,489)				(97,992)
Property and equipment, net	138,314				181,806
Build-to-suit lease arrangements included in Buildings	31,300		$ 31,100		62,100
Cost incurred to date	80,800				82,300
Depreciation and amortization of property and equipment	6,753	$ 8,604
Capitalized interest to date	2,800				4,200
Total non-cancelable minimum lease payments, pre adoption			32,900
Facility financing obligation	35,976		35,700		$ 71,689
Deferred rent			$ 1,800
Gain on derecognition	4,936
Loss on impairment	7,448
Arlington Fulfillment Center [Member]
Property and equipment, net
Property and equipment, net				$ 11,500
Total non-cancelable minimum lease payments, pre adoption				2,200
Fair value of long-lived assets				$ 4,100
Loss on impairment	7,400
Scenario, Plan [Member]
Property and equipment, net
Termination fee	$ 1,500