Stockholders' Equity (Summary Of Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 18,472	$ 15,705	$ 56,254	$ 43,505
Income tax benefit	(7,128)	(5,228)	(21,709)	(16,066)
Total stock-based compensation after income taxes	11,344	10,477	34,545	27,439
Fulfillment Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	103	206	260	1,446
Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	690	1,539	2,911	4,273
Technology And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	10,510	7,522	31,550	19,819
General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 7,169	$ 6,438	$ 21,533	$ 17,967