Pension and retirement plans (Fair Value) (Details) - USD ($) $ in Thousands	Jun. 27, 2020	Jun. 29, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 707,800	$ 664,063	$ 659,038
Recurring
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	707,800	664,063
Recurring | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,243	2,441
Recurring | Common Stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	254,917
Recurring | U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		254,139
Recurring | International common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		131,847
Recurring | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	81,817
Recurring | High yield credit and bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	103,925
Recurring | U.S. government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	218,573	97,015
Recurring | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35,325	153,891
Recurring | Other Debt Obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		24,730
Level 1 | Recurring
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,243	2,441
Level 1 | Recurring | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,243	2,441
Level 2 | Recurring
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		661,622
Level 2 | Recurring | U.S. common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		254,139
Level 2 | Recurring | International common stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		131,847
Level 2 | Recurring | U.S. government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		97,015
Level 2 | Recurring | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		153,891
Level 2 | Recurring | Other Debt Obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 24,730
Net Asset Value | Recurring
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	694,557
Net Asset Value | Recurring | Common Stocks
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	254,917
Net Asset Value | Recurring | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	81,817
Net Asset Value | Recurring | High yield credit and bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	103,925
Net Asset Value | Recurring | U.S. government
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	218,573
Net Asset Value | Recurring | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 35,325