Prepaid Expenses and Other Current Assets, Accrued Expenses, Other Current Liabilities, and Other Liabilities - Components of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Prepaid expenses and other current assets:
Deferred costs in transit	$ 104,947	$ 83,652
Prepaid assets	46,177	31,003
Supplier receivable	28,245	31,842
Supplier credits receivable	20,083	17,667
Other current assets	29,269	31,266
Total prepaid expenses and other current assets	$ 228,721	$ 195,430