Basis of Presentation Additional Information (Detail)	6 Months Ended
Jun. 30, 2018
Revenue From Contract With Customer [Abstract]
Revenue recognition for estimated returns, description	Return rates are estimated by using a historical weighted average return rate over a four-year period

In those circumstances in which an entity sells a good for which the buyer has the right of return (other than under warranty provisions), the entity discloses any material changes in its assumptions about estimated returns.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790

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