Fair Value Measurements and Disclosures (Details) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2013		Dec. 29, 2012
Assets:
Marketable Securities	$ 92,890		$ 109,908
Level 1 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents			0
Level 2 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents			0
Level 3 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents			0
Total [Member] | Municipal securities [Member]
Assets:
Cash Equivalents	0		0
Fair Value, Measurements, Recurring [Member] | Cash [Member]
Assets:
Cash Equivalents	43,100		60,200
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Cash Equivalents	748		109
Marketable Securities	20,738		20,568
Total assets	21,486	[1]	20,677	[1]
Liabilities:
Contingent consideration payable	0		0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money market funds [Member]
Assets:
Cash Equivalents	748		109
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial paper [Member]
Assets:
Cash Equivalents	0		0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury securities and U.S. Government agency securities [Member]
Assets:
Marketable Securities	20,738		20,568
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial paper, corporate debt securities and municipal securities [Member]
Assets:
Marketable Securities	0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Cash Equivalents	0		2,600
Marketable Securities	28,319		26,425
Total assets	28,319	[1]	29,025	[1]
Liabilities:
Contingent consideration payable	0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money market funds [Member]
Assets:
Cash Equivalents	0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial paper [Member]
Assets:
Cash Equivalents	0		2,600
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury securities and U.S. Government agency securities [Member]
Assets:
Marketable Securities	0		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial paper, corporate debt securities and municipal securities [Member]
Assets:
Marketable Securities	28,319		26,425
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets:
Cash Equivalents	0		0
Marketable Securities	0		0
Total assets	0	[1]	0	[1]
Liabilities:
Contingent consideration payable	2,772		2,462
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Money market funds [Member]
Assets:
Cash Equivalents	0		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial paper [Member]
Assets:
Cash Equivalents	0		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Municipal securities [Member]
Assets:
Cash Equivalents	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury securities and U.S. Government agency securities [Member]
Assets:
Marketable Securities	0		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial paper, corporate debt securities and municipal securities [Member]
Assets:
Marketable Securities	0		0
Fair Value, Measurements, Recurring [Member] | Total [Member]
Assets:
Cash Equivalents	748		2,709
Marketable Securities	49,057		46,993
Total assets	49,805	[1]	49,702	[1]
Liabilities:
Contingent consideration payable	2,772		2,462
Fair Value, Measurements, Recurring [Member] | Total [Member] | Money market funds [Member]
Assets:
Cash Equivalents	748		109
Fair Value, Measurements, Recurring [Member] | Total [Member] | Commercial paper [Member]
Assets:
Cash Equivalents	0		2,600
Fair Value, Measurements, Recurring [Member] | Total [Member] | U.S. Treasury securities and U.S. Government agency securities [Member]
Assets:
Marketable Securities	20,738		20,568
Fair Value, Measurements, Recurring [Member] | Total [Member] | Commercial paper, corporate debt securities and municipal securities [Member]
Assets:
Marketable Securities	$ 28,319		$ 26,425

[1] Excludes $43.1 million and $60.2 million held in operating accounts as of September 28, 2013, and December 29, 2012, respectively.