Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Jan. 02, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	$ 153,961	$ 128,901
Total long-term investments	5,196	7,126
Assets and liabilities measured at fair value on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	69,432	37,721
Total short-term investments	12,416
Total assets at fair value	81,848	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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	69,432	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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	12,416
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	11,057	17,293
Total short-term investments	141,545	128,901
Derivative instruments	1,808	92
Other assets, net	1,808	92
Total assets at fair value	154,410	146,286
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	7,153	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
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		11,272
Total short-term investments	5,233	11,176
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	3,904	1,577
Total short-term investments	79,702	93,516
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Variable-rate demand notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	16,400	8,995
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	8,173
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | US government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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) | International government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	1,001	2,220
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	31,036	996
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long-term investments	5,196	7,126
Total assets at fair value	5,196	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:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, current		4,749
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3) | Other non-current liabilities:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, noncurrent		9,324
Assets and liabilities measured at fair value on recurring basis | Significant Unobservable Inputs (Level 3) | Auction rate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long-term investments	5,196	7,126
Fair Value | Assets and liabilities measured at fair value on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	80,489	55,014
Total short-term investments	153,961	128,901
Total long-term investments	5,196	7,126
Derivative instruments	1,808	92
Other assets, net	1,808	92
Total assets at fair value	241,454	191,133
Total liabilities at fair value		14,073
Fair Value | Assets and liabilities measured at fair value on recurring basis | Accrued expenses:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, current		4,749
Fair Value | Assets and liabilities measured at fair value on recurring basis | Other non-current liabilities:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, noncurrent		9,324
Fair Value | Assets and liabilities measured at fair value on recurring basis | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	69,432	37,721
Fair Value | Assets and liabilities measured at fair value on recurring basis | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	7,153	2,845
Total short-term investments		8,000
Fair Value | Assets and liabilities measured at fair value on recurring basis | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		11,272
Total short-term investments	5,233	11,176
Fair Value | Assets and liabilities measured at fair value on recurring basis | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	3,904	1,577
Total short-term investments	79,702	93,516
Fair Value | Assets and liabilities measured at fair value on recurring basis | Variable-rate demand notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	16,400	8,995
Fair Value | Assets and liabilities measured at fair value on recurring basis | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	8,173
Fair Value | Assets and liabilities measured at fair value on recurring basis | US government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents		1,599
Total short-term investments		3,998
Fair Value | Assets and liabilities measured at fair value on recurring basis | International government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	1,001	2,220
Fair Value | Assets and liabilities measured at fair value on recurring basis | Auction rate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long-term investments	5,196	7,126
Fair Value | Assets and liabilities measured at fair value on recurring basis | U.S. government bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	12,416
Fair Value | Assets and liabilities measured at fair value on recurring basis | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total short-term investments	$ 31,036	$ 996