Accrued Expenses And Other Liabilities (Schedule Of Accrued Expenses & Other Current Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Accrued compensation and benefits	$ 32,494		$ 34,955
Professional services	15,031		10,835
Accrued rent and occupancy	9,309		8,535
Fulfillment, freight, and duties	12,499		6,921
Royalties payable and deferred revenue	4,420		6,193
Sales/use and value added taxes payable	11,733		3,509
Return liabilities	8,696		0
Other	11,606		13,498
Total accrued expenses and other liabilities	105,788	$ 87,802	84,446
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Other	$ 3,000		$ 3,000