Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Apr. 02, 2016	Jan. 02, 2016
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	$ 126,690	$ 114,085
Total short-term investments	126,824	128,901
Total long-term investments	6,845	7,126
Assets and liabilities measured at fair value on recurring basis
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	50,493	55,014
Total short-term investments	126,824	128,901
Total long-term investments	6,845	7,126
Derivative instruments		92
Other assets, net		92
Total assets at fair value	184,162	191,133
Total liabilities at fair value	129	14,073
Assets and liabilities measured at fair value on recurring basis | Accrued expenses:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration, current		4,749
Assets and liabilities measured at fair value on recurring basis | Other non-current liabilities:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration, noncurrent		9,324
Derivative instruments	129
Assets and liabilities measured at fair value on recurring basis | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	40,720	37,721
Assets and liabilities measured at fair value on recurring basis | Certificates of deposit
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,849	2,845
Total short-term investments		8,000
Assets and liabilities measured at fair value on recurring basis | Commercial paper
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	1,200	11,272
Total short-term investments	2,489	11,176
Assets and liabilities measured at fair value on recurring basis | Municipal bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	5,724	1,577
Total short-term investments	85,709	93,516
Assets and liabilities measured at fair value on recurring basis | Variable-rate demand notes
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	18,395	8,995
Assets and liabilities measured at fair value on recurring basis | Asset-backed securities
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	3,998
Assets and liabilities measured at fair value on recurring basis | International government bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	2,221	2,220
Assets and liabilities measured at fair value on recurring basis | US government agency
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents		1,599
Total short-term investments		3,998
Assets and liabilities measured at fair value on recurring basis | Corporate bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	8,003	996
Assets and liabilities measured at fair value on recurring basis | U.S. government bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	6,009
Assets and liabilities measured at fair value on recurring basis | Auction rate securities
Financial assets and liabilities measured at fair value on a recurring basis
Total long-term investments	6,845	7,126
Assets and liabilities measured at fair value on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	40,720	37,721
Total short-term investments	6,009
Total assets at fair value	46,729	37,721
Assets and liabilities measured at fair value on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	40,720	37,721
Assets and liabilities measured at fair value on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	6,009
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	9,773	17,293
Total short-term investments	120,815	128,901
Derivative instruments		92
Other assets, net		92
Total assets at fair value	130,588	146,286
Total liabilities at fair value	129
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Other non-current liabilities:
Financial assets and liabilities measured at fair value on a recurring basis
Derivative instruments	129
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Certificates of deposit
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	2,849	2,845
Total short-term investments		8,000
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Commercial paper
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	1,200	11,272
Total short-term investments	2,489	11,176
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Municipal bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	5,724	1,577
Total short-term investments	85,709	93,516
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Variable-rate demand notes
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	18,395	8,995
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	3,998
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | International government bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	2,221	2,220
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | US government agency
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents		1,599
Total short-term investments		3,998
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Corporate bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	8,003	996
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities measured at fair value on a recurring basis
Total long-term investments	6,845	7,126
Total assets at fair value	6,845	7,126
Total liabilities at fair value		14,073
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3) | Accrued expenses:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration, current		4,749
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3) | Other non-current liabilities:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration, noncurrent		9,324
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3) | Auction rate securities
Financial assets and liabilities measured at fair value on a recurring basis
Total long-term investments	$ 6,845	$ 7,126