Pension and retirement plans (Pension Plans) (Details) - Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Jun. 27, 2015	Jun. 28, 2014	Jun. 29, 2013
Changes in benefit obligations:
Benefit obligations at beginning of year	$ 457,167	$ 391,880
Service cost	39,492	36,733	$ 36,920
Interest cost	17,797	17,155	14,653
Actuarial loss (gain)	21,796	34,726
Benefits paid	(22,846)	(23,327)
Benefit obligations at end of year	513,406	457,167	391,880
Change in plan assets:
Fair value of plan assets at beginning of year	449,960	365,373
Actual return on plan assets	17,294	67,914
Benefits paid	(22,846)	(23,327)
Current year-to-date contributions	40,000	40,000
Fair value of plan assets at end of year	484,408	449,960	$ 365,373
Funded status of the plan recognized as a non-current asset (liability)	(28,998)	(7,207)
Amounts recognized in accumulated other comprehensive income:
Unrecognized net actuarial loss	185,819	158,103
Unamortized prior service credit	(4,476)	(6,050)
Amount recognized in accumulated other comprehensive income	181,343	152,053
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net actuarial (gain) loss	40,723	(2,280)
Amortization of net actuarial loss	(13,007)	(12,686)
Amortization of prior service credit	1,573	1,573
Other changes in plan assets and benefit obligations recognized in other comprehensive income	$ 29,289	$ (13,393)
Weighted average assumptions used to calculate actuarial present values of benefit obligations
Discount rate	4.30%	4.00%
Weighted average assumptions used to determine net benefit costs
Discount rate	4.00%	4.50%
Expected return on plan assets	8.50%	8.50%