Financing (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Sep. 30, 2017
Line of Credit Facility [Line Items]
Percent added to Adjusted LIBOR rate for one month interest period	1.00%
Short-term borrowings	$ 5,000		$ 0
Commitment fees incurred on credit facility	$ 79	$ 101
Annual excess cash flow percentage per credit agreement	50.00%
Net cash proceed percentage per credit agreement	100.00%
Alternate base rate
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	2.25%
Minimum
Line of Credit Facility [Line Items]
Line of credit facility, commitment fees payable, percent	0.25%
Minimum | Alternate base rate
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	1.75%
Maximum
Line of Credit Facility [Line Items]
Line of credit facility, commitment fees payable, percent	0.40%
Revolving credit facility
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity	$ 120,000
Maximum borrowing capacity	120,000
Short-term borrowings	5,000		0
Letters of credit outstanding, amount	43,381		37,811
Line of credit facility, remaining borrowing capacity	$ 71,619		$ 82,189
Revolving credit facility | London interbank offered rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Term loan B facility
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity	$ 460,000
Weighted average interest rate	4.54%
Principal amount, amortization percentage	1.00%		1.00%
Eurocurrency borrowing | London interbank offered rate (LIBOR)
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	3.00%
Eurocurrency term loans
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	3.25%
Eurocurrency term loans | London interbank offered rate (LIBOR)
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	1.44%
Eurocurrency term loans | Minimum | London interbank offered rate (LIBOR)
Line of Credit Facility [Line Items]
Effective interest rate applicable to outstanding credit facility (in hundredths)	0.75%