Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Provision for estimated goods returns	$ 300,000	$ 234,000
Allowance for doubtful accounts	242,000	270,000
Advertising expense	$ 31,000,000	$ 27,000,000	$ 23,000,000
Finite-Lived intangible asset, useful life	3 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Finite-Lived intangible asset, useful life	2 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Finite-Lived intangible asset, useful life	7 years