Segment Reporting Segment Reporting (Details)	3 Months Ended		9 Months Ended
	Jan. 27, 2018 USD ($)	Jan. 28, 2017 USD ($)	Jan. 27, 2018 USD ($)	Jan. 28, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments			2
Deferred Compensation Arrangement with Individual, Compensation Expense			$ 5,000,000
Revenue, Net	$ 603,391,000	$ 521,624,000	1,845,963,000	$ 1,531,532,000
Gross Profit	146,535,000	115,925,000	427,806,000	334,852,000
Depreciation and amortization expense	17,007,000	13,149,000	48,728,000	39,057,000
Operating Income (Loss)	(295,625,000)	5,198,000	(267,908,000)	9,196,000
Interest Income (Expense), Net	(2,954,000)	(679,000)	(7,828,000)	(1,975,000)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(298,579,000)	4,519,000	(275,736,000)	7,221,000
Goodwill, Impairment Loss	313,130		313,130,000
BNC [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Gross	506,460,000		1,518,224,000
Gross Profit	117,413,000		337,875,000
Depreciation and amortization expense	15,411,000		43,879,000
Operating Income (Loss)	(308,954,000)		(310,004,000)
MBS [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Gross	138,927,000	0	413,579,000	0
Gross Profit	34,949,000	0	95,713,000	0
Depreciation and amortization expense	1,596,000	0	4,849,000	0
Operating Income (Loss)	19,156,000	0	47,878,000	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Gross	(41,996,000)	0	(85,840,000)	0
Gross Profit	(5,827,000)	0	(5,782,000)	0
Operating Income (Loss)	$ (5,827,000)	$ 0	$ (5,782,000)	$ 0