Financing Arrangements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016
Short-term borrowings [Abstract]
Line of credit facility, available borrowing capacity	$ 1,000,000
Maturities of the notes, maximum	397 days
Commercial paper program, notes outstanding	$ 137,500	$ 163,300
Commercial paper program, weighted average interest rate	1.85%	0.97%
Unsecured Committed [Member]
Short-term borrowings [Abstract]
Maturity Date, Line of credit facility	Mar. 30, 2020
Line of credit facility, available borrowing capacity	$ 1,000,000
Commitment fee based on unused portion of line of credit facility	0.12%
Interest rate under line of credit facility	Eurocurrency Rate plus 1.125%.
Unsecured Uncommitted [Member]
Short-term borrowings [Abstract]
Line of credit facility, available borrowing capacity	$ 146,000
Weighted average interest rates of outstanding borrowings	4.32%	8.17%