Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jul. 04, 2015	Jan. 03, 2015
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	$ 125,051	$ 141,706
Total short-term investments	147,556	193,489
Total long-term investments	7,179	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	43,689	72,415
Total short-term investments		650
Total assets at fair value	43,689	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	43,689	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	15,913	17,147
Total short-term investments	147,556	192,839
Derivative instruments		331
Other assets, net		331
Total assets at fair value	163,469	210,317
Total liabilities at fair value	35
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	35
Total liabilities at fair value	35
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	5,547	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	1,199	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	543	1,757
Total short-term investments	122,199	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	14,495	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	2,237	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	9,823	1,101
Total short-term investments	7,426	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	7,179	7,419
Total assets at fair value	7,179	7,419
Total liabilities at fair value	15,092	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	3,965	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	11,127	14,150
Total liabilities at fair value	11,127
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	7,179	7,419
Assets and liabilities measured at fair value on recurring basis | Fair Value
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	59,602	89,562
Total short-term investments	147,556	193,489
Total long-term investments	7,179	7,419
Derivative instruments		331
Other assets, net		331
Total assets at fair value	214,337	290,801
Total liabilities at fair value	15,127	18,438
Assets and liabilities measured at fair value on recurring basis | Fair Value | Accrued expenses:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration	3,965	4,288
Assets and liabilities measured at fair value on recurring basis | Fair Value | Other non-current liabilities:
Financial assets and liabilities measured at fair value on a recurring basis
Contingent consideration	11,127	14,150
Derivative instruments	35
Total liabilities at fair value	11,162
Assets and liabilities measured at fair value on recurring basis | Fair Value | Money market funds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	43,689	71,415
Assets and liabilities measured at fair value on recurring basis | Fair Value | Certificates of deposit
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	5,547	7,739
Total short-term investments		250
Assets and liabilities measured at fair value on recurring basis | Fair Value | Commercial paper
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents		5,348
Total short-term investments	1,199	8,995
Assets and liabilities measured at fair value on recurring basis | Fair Value | Municipal bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	543	1,757
Total short-term investments	122,199	129,152
Assets and liabilities measured at fair value on recurring basis | Fair Value | Variable-rate demand notes
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	14,495	12,915
Assets and liabilities measured at fair value on recurring basis | Fair Value | 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 | Fair Value | International government bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	2,237	2,516
Assets and liabilities measured at fair value on recurring basis | Fair Value | 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 | Fair Value | Corporate bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	9,823	1,101
Total short-term investments	7,426	33,033
Assets and liabilities measured at fair value on recurring basis | Fair Value | 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 | Fair Value | Auction rate securities
Financial assets and liabilities measured at fair value on a recurring basis
Total long-term investments	$ 7,179	$ 7,419