Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Oct. 01, 2016	Jan. 02, 2016
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	$ 131,139	$ 128,901
Total long-term investments	6,980	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	39,457	55,014
Total short-term investments	131,139	128,901
Total long-term investments	6,980	7,126
Derivative instruments	72	92
Other assets, net	72	92
Total assets at fair value	177,648	191,133
Total liabilities at fair value		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
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	36,200	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	2,956	2,845
Total short-term investments		8,000
Assets and liabilities measured at fair value on recurring basis | U.S. 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 | Municipal bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	301	1,577
Total short-term investments	60,682	93,516
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	22,306	996
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	15,324	8,995
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	14,392
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	10,961
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		11,272
Total short-term investments	6,466	11,176
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	1,008	2,220
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	6,980	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	36,200	37,721
Total short-term investments	14,392
Total assets at fair value	50,592	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	36,200	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	14,392
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	3,257	17,293
Total short-term investments	116,747	128,901
Derivative instruments	72	92
Other assets, net	72	92
Total assets at fair value	120,076	146,286
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	2,956	2,845
Total short-term investments		8,000
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | U.S. 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) | Municipal bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	301	1,577
Total short-term investments	60,682	93,516
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	22,306	996
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	15,324	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	10,961
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		11,272
Total short-term investments	6,466	11,176
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	1,008	2,220
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	6,980	7,126
Total assets at fair value	6,980	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	$ 6,980	$ 7,126