Business Segments - Reconciliation of Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 25, 2017	Feb. 27, 2016	Feb. 25, 2017	Feb. 27, 2016
Segment Reporting [Abstract]
Net income	$ 15,278	$ 9,354	$ 27,016	$ 17,912
Interest expense	5,178	0	6,306	0
Provision for income taxes	7,916	4,131	13,536	8,467
Depreciation	1,848	1,393	3,428	2,763
Amortization of intangible assets	10,367	0	12,418	0
EBITDA	40,587	14,878	62,704	29,142
Postretirement health care benefit income	(11,983)	(1,593)	(24,796)	(2,938)
Transaction costs	463	0	5,925	0
Non-operating expense (income)	4	18	(83)	(117)
Adjusted EBITDA	$ 29,071	$ 13,303	$ 43,750	$ 26,087