Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Oct. 03, 2015	Jan. 03, 2015
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	$ 135,640	$ 141,706
Total short-term investments	112,670	193,489
Total long-term investments	7,240	7,419
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	67,219	89,562
Total short-term investments	112,670	193,489
Total long-term investments	7,240	7,419
Derivative instruments		331
Other assets, net		331
Total assets at fair value	187,129	290,801
Total liabilities at fair value	13,591	18,438
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	4,070	4,288
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	9,192	14,150
Derivative instruments	329
Total liabilities at fair value	9,521
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	63,316	71,415
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	3,903	7,739
Total short-term investments		250
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		5,348
Total short-term investments		8,995
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		1,757
Total short-term investments	98,741	129,152
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	9,495	12,915
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		5,377
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	2,235	2,516
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		1,202
Total short-term investments		601
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 cash equivalents		1,101
Total short-term investments	2,199	33,033
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 cash equivalents		1,000
Total short-term investments		650
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	7,240	7,419
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	63,316	72,415
Total short-term investments		650
Total assets at fair value	63,316	73,065
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	63,316	71,415
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 cash equivalents		1,000
Total short-term investments		650
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	3,903	17,147
Total short-term investments	112,670	192,839
Derivative instruments		331
Other assets, net		331
Total assets at fair value	116,573	210,317
Total liabilities at fair value	329
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	329
Total liabilities at fair value	329
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	3,903	7,739
Total short-term investments		250
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		5,348
Total short-term investments		8,995
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		1,757
Total short-term investments	98,741	129,152
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	9,495	12,915
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		5,377
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	2,235	2,516
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		1,202
Total short-term investments		601
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 cash equivalents		1,101
Total short-term investments	2,199	33,033
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	7,240	7,419
Total assets at fair value	7,240	7,419
Total liabilities at fair value	13,262	18,438
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	4,070	4,288
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	9,192	14,150
Total liabilities at fair value	9,192
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	$ 7,240	$ 7,419