Disaggregation of Revenue - Schedule of Revenue Disaggregation for Customer Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Disaggregation Of Revenue [Line Items]
Total revenues	$ 238,085	$ 206,906	$ 1,080,514	$ 941,839
Retail [Member] | Residential [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	120,186	123,157	605,827	568,644
Retail [Member] | Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	76,215	53,502	284,541	232,165
Retail [Member] | Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	25,270	18,254	86,512	73,508
Retail [Member] | Agricultural [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	6,181	5,317	30,890	28,885
Retail [Member] | Government [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	9,289	6,659	44,761	38,594
Wholesale [Member]
Disaggregation Of Revenue [Line Items]
Total revenues	$ 944	$ 17	$ 27,983	$ 43