Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Apr. 04, 2015	Jan. 03, 2015
Financial assets and liabilities measured at fair value on a recurring basis
Total cash equivalents	$ 112,710	$ 141,706
Total short-term investments	148,795	193,489
Total long-term investments	7,401	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	58,808	72,415
Total short-term investments		650
Total assets at fair value	58,808	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	58,808	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	5,600	17,147
Total short-term investments	148,795	192,839
Derivative instruments		331
Other assets, net		331
Total assets at fair value	154,395	210,317
Total liabilities at fair value	165
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	165
Total liabilities at fair value	165
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	5,148	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	4,898	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	452	1,757
Total short-term investments	122,917	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	8,615	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	2,248	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	10,117	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	7,401	7,419
Total assets at fair value	7,401	7,419
Total liabilities at fair value	14,804	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	3,225	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	11,579	14,150
Total liabilities at fair value	11,579
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	7,401	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	64,408	89,562
Total short-term investments	148,795	193,489
Total long-term investments	7,401	7,419
Derivative instruments		331
Other assets, net		331
Total assets at fair value	220,604	290,801
Total liabilities at fair value	14,969	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	3,225	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	11,579	14,150
Derivative instruments	165
Total liabilities at fair value	11,744
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	58,808	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	5,148	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	4,898	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	452	1,757
Total short-term investments	122,917	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	8,615	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	2,248	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		1,101
Total short-term investments	10,117	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	$ 7,401	$ 7,419