Note 17 - Pension and Postretirement Benefits (Details Textual) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2020	Feb. 23, 2020	Aug. 25, 2019	May 29, 2022	May 30, 2021	May 31, 2020	Dec. 31, 2019	May 26, 2019
Defined Benefit Plan, Recognized Net Actuarial Gain (Loss), Percentage				10.00%
Fair Value Investments Ability To Impose Customary Redemption Gates				$ 29,400
Fair Value Investments Impose Customary Redemption Gates				0
Defined Contribution Plan, Cost				$ 57,900	$ 47,600	$ 49,900
Maximum [Member]
Red Zone Multiemployer Plans Funded Percentage				65.00%
Yellow Zone Multiemployer Plans Funded Percentage				80.00%
Green Zone Multiemployer Plan Funded Percentage				80.00%
Minimum [Member]
Percentage Providing More Than Plans Contribution				5.00%
Private Equity Funds [Member]
Unfunded Commitment For Additional Investment				$ 35,000
Natural Resources Funds [Member]
Unfunded Commitment For Additional Investment				$ 10,400
Fixed Income Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				90.00%
Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				10.00%
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment				$ (0)	$ (200)	(800)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.48%	3.04%
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax				$ 0	$ 200
Defined Benefit Plan, Plan Assets, Payment for Settlement				(0)	(0)
Defined Benefit Plan, Accumulated Benefit Obligation, (Increase) Decrease for Settlement and Curtailment		$ 79,800
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment				0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)				503,100	37,400
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)				(366,100)	194,600
Defined Benefit Plan, Accumulated Benefit Obligation				3,130,000	3,740,000
Defined Benefit Plan Recognized Net Actuarial Gain Loss				2,900	800	44,800
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year				12,400
Pension Plan [Member] | Facility Closing [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment			$ 600
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate			3.13%					3.90%
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment			$ 12,300
Pension Plan [Member] | Hourly Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	$ 200
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.96%							3.86%
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax	$ 4,300
Pension Plan [Member] | Salaried Pension Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate							3.37%	3.89%
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax		2,100
Defined Benefit Plan, Plan Assets, Payment for Settlement		$ 154,600
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment				$ (0)	$ (0)	$ (0)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.24%	2.51%
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax				$ 0	$ (500)
Defined Benefit Plan, Plan Assets, Payment for Settlement				(0)	300
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Curtailment				0	0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)				9,500	2,300
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)				100	$ 200
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year				$ 8,100