CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - shares	3 Months Ended
Mar. 31, 2019	Apr. 01, 2018
Treasury Stock, Shares, Acquired	58,637	33,805
Common Class A
Stock Issued During Period, Shares, Employee Stock Purchase Plans	168,610	94,184

Number of shares issued during the period as a result of an employee stock purchase plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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Name:	us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration