Stockholders' Equity (Summary Of Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 18,450	$ 15,536	$ 37,782	$ 27,800
Income tax benefit	(7,120)	(5,973)	(14,580)	(10,720)
Total stock-based compensation after income taxes	11,330	9,563	23,202	17,080
Fulfillment Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	90	679	157	1,240
Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	817	1,485	2,221	2,734
Technology And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	10,440	7,005	21,040	12,297
General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before income taxes	$ 7,103	$ 6,367	$ 14,364	$ 11,529