Disaggregation of Revenue - Schedule of Revenue Disaggregation for Customer Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 28, 2019
Disaggregation Of Revenue [Line Items]
Total revenues	$ 1,288,755	$ 1,107,897	$ 1,267,705
Retail [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	703,263	654,265	731,468
Retail [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	353,365	283,021	333,078
Retail [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	111,723	92,969	104,992
Retail [Member] | Agricultural [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	37,873	33,718	39,937
Retail [Member] | Government [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	51,917	43,441	53,764
Wholesale [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 30,614	$ 483	$ 4,466