Credit Agreement (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 29, 2013
Line of Credit Facility [Line Items]
Senior credit facility, maximum borrowing capacity	$ 250
Line of credit facility increase option	150
Line of credit facility, expiration date	Oct. 31, 2016
Percentage of additional interest added to LIBOR minimum	0.40%
Percentage of additional interest added to LIBOR maximum	1.00%
Percentage of additional interest added to LIBOR	0.50%
Commitment fee minimum	0.08%
Commitment fee maximum	0.20%
Commitment fee for unused capacity	0.10%
Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Letters of credit under senior credit facility amount outstanding	73.9
Swing Loan [Member]
Line of Credit Facility [Line Items]
Swing loan maximum borrowing capacity	$ 20