Stockholders' Equity (Summary Of Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 19,332	$ 12,264
Income tax benefit	(6,708)	(4,744)
Total stock-based compensation after income taxes	12,624	7,520
Fulfillment Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	67	560
Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	1,404	1,249
Technology And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	10,600	5,292
General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 7,261	$ 5,163