Accrued Expenses And Other Liabilities (Schedule Of Accrued Expenses & Other Current Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Accrued compensation and benefits	$ 40,960		$ 34,955
Professional services	11,042		10,835
Accrued rent and occupancy	7,826		8,535
Fulfillment, freight, and duties	8,647		6,921
Royalties payable and deferred revenue	3,940		6,193
Sales/use and value added taxes payable	7,342		3,509
Return liabilities	7,261		0
Other	12,775		13,498
Total accrued expenses and other liabilities	99,793	$ 87,802	84,446
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Other	$ 3,000		$ 3,000