Summary Of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Allowance for uncollectible accounts	$ 0.4	$ 0.1
Software amortization	16.4	14.2	11.0
Unamortized software	75.2	74.4
Customer relationships
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	14 years	13 years
Customer relationships | Minimum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	10 years
Customer relationships | Maximum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	15 years
Other Intangibles
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	6 years	6 years
Other Intangibles | Minimum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	1 year
Other Intangibles | Maximum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	15 years
Software technology | Minimum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	3 years
Software technology | Maximum
Summary Of Significant Accounting Policies [Line Items]
Intangible assets useful life (in years)	10 years
Warehouse equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	4 years
Warehouse equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	15 years
Building and improvements | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	5 years
Building and improvements | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	40 years
Computer equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	3 years
Computer equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	8 years
Furniture and fixtures | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	3 years
Furniture and fixtures | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	8 years
Office equipment and other | Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	3 years
Office equipment and other | Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life (in years)	8 years
Warehouse Facilities | Minimum
Summary Of Significant Accounting Policies [Line Items]
Terms of lease (in years)	1 year
Warehouse Facilities | Maximum
Summary Of Significant Accounting Policies [Line Items]
Terms of lease (in years)	15 years
Transportation And Material Handling Equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Terms of lease (in years)	3 years
Transportation And Material Handling Equipment | Maximum
Summary Of Significant Accounting Policies [Line Items]
Terms of lease (in years)	10 years
Foreign Subsidiaries
Summary Of Significant Accounting Policies [Line Items]
Cash, cash-equivalents, short-term investments, and marketable securities	31.5	22.2
S,G&A Expenses
Summary Of Significant Accounting Policies [Line Items]
Shipping and handling costs	576.8	528.2	372.5
International Segment | Acquisition-related and Exit and Realignment Charges | Information Systems Related Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Restructuring and Related Cost, Accelerated Amortization	$ 6.0