Fair Value Measurements and Disclosures (Details) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2014	Dec. 28, 2013
Assets:
Total marketable securities	$ 87,361	$ 92,862
Fair Value, Measurements, Recurring [Member] | Cash [Member]
Assets:
Total cash equivalents	37,600	43,100
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Total cash equivalents	403	876
Total marketable securities	5,009	5,036
Total assets	5,412	5,912
Liabilities:
Contingent consideration payable	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money market funds [Member]
Assets:
Total cash equivalents	403	876
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury, U.S. Government and U.S. Government agency debt securities [Member]
Assets:
Total marketable securities	5,009	5,036
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial paper [Member]
Assets:
Total cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial paper, municipal securities and corporate debt securities [Member]
Assets:
Total marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Total cash equivalents	0	750
Total marketable securities	44,365	43,061
Total assets	44,365	43,811
Liabilities:
Contingent consideration payable	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money market funds [Member]
Assets:
Total cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury, U.S. Government and U.S. Government agency debt securities [Member]
Assets:
Total marketable securities	13,416	11,980
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial paper [Member]
Assets:
Total cash equivalents	0	750
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial paper, municipal securities and corporate debt securities [Member]
Assets:
Total marketable securities	30,949	31,081
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets:
Total cash equivalents	0	0
Total marketable securities	0	0
Total assets	0	0
Liabilities:
Contingent consideration payable	2,588	2,783
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Money market funds [Member]
Assets:
Total cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury, U.S. Government and U.S. Government agency debt securities [Member]
Assets:
Total marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial paper [Member]
Assets:
Total cash equivalents	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial paper, municipal securities and corporate debt securities [Member]
Assets:
Total marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Total [Member]
Assets:
Total cash equivalents	403	1,626
Total marketable securities	49,374	48,097
Total assets	49,777	49,723
Liabilities:
Contingent consideration payable	2,588	2,783
Fair Value, Measurements, Recurring [Member] | Total [Member] | Money market funds [Member]
Assets:
Total cash equivalents	403	876
Fair Value, Measurements, Recurring [Member] | Total [Member] | U.S. Treasury, U.S. Government and U.S. Government agency debt securities [Member]
Assets:
Total marketable securities	18,425	17,016
Fair Value, Measurements, Recurring [Member] | Total [Member] | Commercial paper [Member]
Assets:
Total cash equivalents	0	750
Fair Value, Measurements, Recurring [Member] | Total [Member] | Commercial paper, municipal securities and corporate debt securities [Member]
Assets:
Total marketable securities	$ 30,949	$ 31,081