Debt and Credit Facility (Details 1) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Mar. 29, 2014	Mar. 31, 2018	May 30, 2017	Mar. 12, 2014
Debt Instrument [Line Items]
Net interest rate received (paid) from interest rate swap	$ (642,000)	$ 1,500,000	$ (1,500,000)	$ 2,100,000
Long-term Debt, Current Maturities	499,629,000		499,629,000			$ 499,186,000
Amortization of Debt Discount (Premium)			591,000	1,964,000
Proceeds from Issuance of Long-term Debt			$ 0	745,175,000
Debt Instrument, Description of Variable Rate Basis			three-month London Interbank Offered Rate (LIBOR) plus 91.43 bps
Line of Credit Facility, Expiration Date			Dec. 14, 2021
Line of Credit Facility, Maximum Borrowing Capacity	400,000,000		$ 400,000,000
AdditionalborrowingcapacityfromRevolvingCreditFacility	150,000,000		150,000,000
Line of Credit Facility, Average Outstanding Amount			0
Long-term Debt, Excluding Current Maturities	1,201,884,000		1,201,884,000			1,214,440,000
Two Point and Nine Five Percent 2024 Senior Debentures [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 750,000,000		$ 750,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.95%		2.95%
Two And One Two Five Percent 2019 Senior Debentures [Member]
Debt Instrument [Line Items]
Discount Percent of Par								99.477%
Debt Instrument, Face Amount	$ 500,000,000		$ 500,000,000			500,000,000
Debt Instrument, Unamortized Discount	(229,000)		(229,000)			(501,000)
Debt Issuance Costs, Current, Net	142,000		142,000			313,000
Long-term Debt, Current Maturities	$ 499,629,000		499,629,000			499,186,000
Debt instrument, long term debt, remaining discount amortization period	5 months 15 days
2019 and 2021 Notes Payable [Member]
Debt Instrument [Line Items]
Interest Expense, Debt, Excluding Amortization	$ 6,406,000	6,406,000	12,813,000	12,813,000
Amortization of Debt Issuance Costs	146,000	146,000	292,000	293,000
Amortization of Debt Discount (Premium)	269,000	262,000	535,000	520,000
Interest Expense, Debt	6,821,000	6,814,000	13,640,000	13,626,000
Proceeds from Issuance of Long-term Debt					$ 990,100,000
Debt, Long-term and Short-term, Combined Amount	997,709,000		997,709,000			996,882,000
Two Point and Nine Five Percent 2024 Senior Debentures [Member]
Debt Instrument [Line Items]
Discount Percent of Par							99.887%
Debt Instrument, Face Amount	$ 750,000,000		$ 750,000,000			750,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.95%		2.95%
Debt Instrument, Unamortized Discount	$ (699,000)		$ (699,000)			(755,000)
Debt Issuance Costs, Noncurrent, Net	3,216,000		3,216,000			3,500,000
Long Term Debt, Carrying Value before Hedging Adjustment	746,085,000		746,085,000			745,745,000
Derivative, Amount of Hedged Item	(42,281,000)		(42,281,000)			(29,001,000)
Interest Expense, Debt, Excluding Amortization	6,174,000	4,046,000	12,556,000	5,368,000
Amortization of Debt Issuance Costs	142,000	142,000	284,000	189,000
Amortization of Debt Discount (Premium)	27,000	27,000	56,000	37,000
Interest Expense, Debt	$ 6,343,000	$ 4,215,000	12,896,000	$ 5,594,000
Proceeds from Issuance of Long-term Debt			745,200,000
Debt instrument, long term debt, remaining discount amortization period	5 years 8 months
Long-term Debt, Excluding Current Maturities	$ 703,804,000		703,804,000			716,744,000
Three Point Zero Percent 2021 Senior Debentures [Member]
Debt Instrument [Line Items]
Discount Percent of Par								99.281%
Debt Instrument, Face Amount	500,000,000		500,000,000			500,000,000
Debt Instrument, Unamortized Discount	(1,330,000)		(1,330,000)			(1,593,000)
Debt Issuance Costs, Noncurrent, Net	$ 590,000		590,000			711,000
Debt instrument, long term debt, remaining discount amortization period	2 years 5 months 15 days
Long-term Debt, Excluding Current Maturities	$ 498,080,000		498,080,000			$ 497,696,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	$ 42,300,000		$ 42,300,000