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. 30, 2014	$ 192,748	$ 25,888	$ 31,672	$ 554,496	$ (1,808)	$ (417,500)
Beginning balance (in shares) at Aug. 30, 2014		51,776				(24,727)
Creation/utilization of APIC pool due to stock award	124		124
Issuance of restricted stock	1,410		(1,950)			$ 3,360
Issuance of restricted stock (in shares)						199
Stock-based compensation, net of forfeitures	2,221		2,172			$ 49
Stock-based compensation, net of forfeitures (in shares)						3
Payments for the purchase of common stock	(6,519)					$ (6,519)
Payments for the purchase of common stock (in shares)						(300)
Cash dividends paid on common stock	(9,765)			(9,765)
Prior service cost and actuarial loss, net of tax	(2,917)				(2,917)
Plan amendment, net of tax	2,451				2,451
Change in fair value of interest rate swap, net of tax	0
Net income	41,210			41,210
Ending balance at Aug. 29, 2015	220,963	$ 25,888	32,018	585,941	(2,274)	$ (420,610)
Ending 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
Payments for the purchase of common stock	(3,066)					$ (3,066)
Payments for the purchase 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
Issuance of stock for acquisition	124,066		46,205			$ 77,861
Issuance of stock for acquisition (in shares)						4,586
Stock-based compensation, net of forfeitures (in shares)						5
Payments for the purchase of common stock	(1,531)					$ (1,531)
Payments for the purchase 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)
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)