Pension and retirement plans (Fair Value) (Details) - USD ($) $ in Thousands	Jun. 27, 2015	Jun. 28, 2014	Jun. 29, 2013
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 484,408	$ 449,960	$ 365,373
Level 1 | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,111	3,025
Level 1 | Cash and cash equivalents | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,111	3,025
Fair Value, Inputs, Level 2 [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	482,297	446,935
Fair Value, Inputs, Level 2 [Member] | Equity securities | US Common Stocks [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	287,495	267,741
Fair Value, Inputs, Level 2 [Member] | Equity securities | International Common Stocks [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79,704	71,273
Fair Value, Inputs, Level 2 [Member] | U.S. government agencies [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,912	10,439
Fair Value, Inputs, Level 2 [Member] | U.S. corporate bonds [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	106,186	97,482
Estimate of Fair Value Measurement [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	484,408
Estimate of Fair Value Measurement [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		449,960
Estimate of Fair Value Measurement [Member] | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,111
Estimate of Fair Value Measurement [Member] | Cash and cash equivalents | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,025
Estimate of Fair Value Measurement [Member] | Equity securities | US Common Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	287,495
Estimate of Fair Value Measurement [Member] | Equity securities | US Common Stocks [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		267,741
Estimate of Fair Value Measurement [Member] | Equity securities | International Common Stocks [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	79,704
Estimate of Fair Value Measurement [Member] | Equity securities | International Common Stocks [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		71,273
Estimate of Fair Value Measurement [Member] | U.S. government agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,912
Estimate of Fair Value Measurement [Member] | U.S. government agencies [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10,439
Estimate of Fair Value Measurement [Member] | U.S. corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 106,186
Estimate of Fair Value Measurement [Member] | U.S. corporate bonds [Member] | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 97,482