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Earnings Per Share (Narrative) (Details)
3 Months Ended 6 Months Ended
Mar. 30, 2019
shares
Mar. 31, 2018
shares
Sep. 30, 2017
shares
Jul. 02, 2016
trade_day
shares
Mar. 30, 2019
trade_day
shares
Mar. 31, 2018
shares
Class of Stock [Line Items]            
Antidilutive securities excluded from computation of earnings per share, amount (in shares) 865,000 482,000     791,000 489,000
Equity Component            
Class of Stock [Line Items]            
Threshold consecutive trading days | trade_day       20 20  
Equity Component | Minimum | Common Class A            
Class of Stock [Line Items]            
Convertible, number of equity instruments per contract (in shares)     1.9841 1.9841 1.9841  
Equity Component | Maximum | Common Class A            
Class of Stock [Line Items]            
Convertible, number of equity instruments per contract (in shares)       2.3810 2.3810