Property And Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 396,356	$ 329,487
Accumulated depreciation	(163,377)	(137,526)
Property and equipment, net	232,979	191,961
Warehouse equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	169,083	160,379
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	31,162	31,784
Building and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	87,974	50,225
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	58,046	49,879
Land and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	17,771	17,489
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,539	11,491
Office equipment and other
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 19,781	$ 8,240