Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares [Member]	Additional Paid-In Capital (APIC) [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Beginning balance at Aug. 29, 2015	$ 220,963	$ 25,888	$ 32,018	$ 585,941	$ (2,274)	$ (420,610)
Beginning balance (in shares) at Aug. 29, 2015		51,776				(24,825)
Creation/utilization of APIC pool due to stock award	33		33
Issuance of restricted stock	517		(1,309)			$ 1,826
Issuance of restricted stock (in shares)						108
Stock-based compensation, net of forfeitures	2,058		1,975			$ 83
Stock-based compensation, net of forfeitures (in shares)						5
Repurchase of common stock	(3,066)					$ (3,066)
Repurchase of common stock (in shares)						(163)
Cash dividends paid on common stock	(10,891)			(10,891)
Prior service cost and actuarial loss, net of tax	(4,452)				(4,452)
Plan amendment, net of tax	17,701				17,701
Change in fair value of interest rate swap, net of tax	0
Net income	45,496			45,496
Ending balance at Aug. 27, 2016	268,359	$ 25,888	32,717	620,546	10,975	$ (421,767)
Ending balance (in shares) at Aug. 27, 2016		51,776				(24,875)
Creation/utilization of APIC pool due to stock award	470		470
Issuance of restricted stock	808		(1,821)			$ 2,629
Issuance of restricted stock (in shares)						155
Stock-based compensation, net of forfeitures	2,908		2,830			$ 78
Stock-based compensation, net of forfeitures (in shares)						5
Issuance of stock for acquisition	124,066		46,205			$ 77,861
Issuance of stock for acquisition (in shares)						4,586
Repurchase of common stock	(1,531)					$ (1,531)
Repurchase of common stock (in shares)						(54)
Cash dividends paid on common stock	(12,738)			(12,738)
Prior service cost and actuarial loss, net of tax	(15,387)				(15,387)
Plan amendment, net of tax	3,903				3,903
Change in fair value of interest rate swap, net of tax	(514)				(514)
Reclassification of tax effects					0
Net income	71,330			71,330
Ending balance at Aug. 26, 2017	441,674	$ 25,888	80,401	679,138	(1,023)	$ (342,730)
Ending balance (in shares) at Aug. 26, 2017		51,776				(20,183)
Issuance of restricted stock	87		(1,625)			$ 1,712
Issuance of restricted stock (in shares)						101
Stock-based compensation, net of forfeitures	7,484		7,406			$ 78
Stock-based compensation, net of forfeitures (in shares)						5
Repurchase of common stock	(6,481)					$ (6,481)
Repurchase of common stock (in shares)						(169)
Issuance of stock under ESPP	88		41			$ 47
Issuance of stock under ESPP (in shares)						3
Cash dividends paid on common stock	(12,738)			(12,738)
Prior service cost and actuarial loss, net of tax	27				27
Change in fair value of interest rate swap, net of tax	1,947				1,947
Reclassification of tax effects	0			59	(59)
Net income	102,357			102,357
Ending balance at Aug. 25, 2018	$ 534,445	$ 25,888	$ 86,223	$ 768,816	$ 892	$ (347,374)
Ending balance (in shares) at Aug. 25, 2018		51,776				(20,243)