Retirement and Welfare Plans - Defined Benefit and Defined Contribution (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 25, 2015	Apr. 26, 2014
Components of net periodic pension cost
Other	$ 318	$ 124	$ 223
Total retirement costs (excluding non-qualified defined benefit retirement plan)	14,363	11,536	11,189
401(k)
Components of net periodic pension cost
Defined contribution plan cost	6,657	6,270	5,802
PCRP
Components of net periodic pension cost
Defined contribution plan cost	3,088	1,377	2,513
Defined benefit pension plan for factory hourly employees
Changes in plan assets and benefit obligations recognized in accumulated other comprehensive loss (pre-tax)
Beginning of year net actuarial loss	37,602	39,425
Net current year actuarial (gain) loss	2,249	836
Amortization of actuarial loss	(3,001)	(2,659)
End of year net actuarial loss	36,850	37,602	39,425
Unrecognized actuarial losses expected to be amortized in fiscal 2017	3,100
Components of net periodic pension cost
Service cost	1,358	1,114	1,241
Interest cost	4,938	5,070	4,822
Expected return on plan assets	(4,997)	(5,077)	(6,800)
Net amortization and deferral	3,001	2,658	3,388
Net periodic pension cost	4,300	3,765	2,651
Change in benefit obligation
Benefit obligation at beginning of year	121,080	116,870
Service cost	1,358	1,114	1,241
Interest cost	4,938	5,070	4,822
Actuarial loss	221	3,664
Benefits paid	(10,808)	(5,638)
Administrative expenses	(418)
Benefit obligation at end of year	116,371	121,080	116,870
Change in plan assets
Fair value of plan assets at beginning of year	113,742	111,474
Actual return on plan assets	2,968	7,906
Employer contributions	7,000
Benefits paid	(10,808)	(5,638)
Administrative expenses	(418)
Fair value of plan assets at end of year	112,484	113,742	$ 111,474
Funded status	(3,887)	(7,338)
Other long-term liabilities	$ (3,887)	$ (7,338)
Actuarial assumptions for the defined benefit pension plan
Discount rate used to determine benefit obligations (as a percent)	4.10%	4.20%	4.40%
Discount rate used to determine net benefit cost (as a percent)	4.20%	4.40%	4.00%
Long-term rate of return (as a percent)	4.30%	4.70%	4.70%
Pension assets
Expected contributions during fiscal 2016	$ 2,000
Expected benefit payments
2017	6,311
2018	6,451
2019	6,608
2020	6,752
2021	6,874
2022 to 2026	35,659
Total	68,655
Defined benefit pension plan for factory hourly employees | Level 1
Change in plan assets
Fair value of plan assets at beginning of year	23,269
Fair value of plan assets at end of year	22,744	$ 23,269
Defined benefit pension plan for factory hourly employees | Level 2
Change in plan assets
Fair value of plan assets at beginning of year	90,473
Fair value of plan assets at end of year	$ 89,740	90,473
Defined benefit pension plan for factory hourly employees | Fixed rate investments
Pension assets
Strategic asset allocation (as a percent)	90.00%
Defined benefit pension plan for factory hourly employees | Cash and equivalents | Level 1
Change in plan assets
Fair value of plan assets at beginning of year	$ 149
Fair value of plan assets at end of year	3,239	149
Defined benefit pension plan for factory hourly employees | Cash and equivalents | Level 2
Change in plan assets
Fair value of plan assets at beginning of year	3,685
Fair value of plan assets at end of year	15,440	3,685
Defined benefit pension plan for factory hourly employees | Equity funds | Level 1
Change in plan assets
Fair value of plan assets at beginning of year	23,120
Fair value of plan assets at end of year	19,505	23,120
Defined benefit pension plan for factory hourly employees | Equity funds | Level 2
Change in plan assets
Fair value of plan assets at beginning of year	7,702
Fair value of plan assets at end of year	42	7,702
Defined benefit pension plan for factory hourly employees | Debt funds | Level 2
Change in plan assets
Fair value of plan assets at beginning of year	79,086
Fair value of plan assets at end of year	$ 74,258	$ 79,086