Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	$ 396,327	$ 153,961
Total long-term investments	5,257	5,196
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	85,090	69,432
Total short-term investments	50,437	12,416
Total assets at fair value	135,527	81,848
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	85,090	69,432
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	50,437	12,416
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	70,297	11,057
Total short-term investments	345,890	141,545
Derivative instruments		1,808
Other assets, net		1,808
Total assets at fair value	416,187	154,410
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	32,183	7,153
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	6,034	3,904
Total short-term investments	78,555	79,702
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	1,498
Total short-term investments	108,828	31,036
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	117,770	16,400
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	25,519	8,173
Assets and liabilities measured at fair value on recurring basis | Significant Other Observable Inputs (Level 2) | Agency bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	7,482
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	30,582
Total short-term investments	6,239	5,233
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	1,497	1,001
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	5,257	5,196
Total assets at fair value	5,257	5,196
Contingent consideration, noncurrent	3,829
Total liabilities at fair value	3,829
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	5,257	5,196
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	155,387	80,489
Total short-term investments	396,327	153,961
Total long-term investments	5,257	5,196
Derivative instruments		1,808
Other assets, net		1,808
Total assets at fair value	556,971	241,454
Contingent consideration, noncurrent	3,829
Total liabilities at fair value	3,829
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	85,090	69,432
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	32,183	7,153
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	6,034	3,904
Total short-term investments	78,555	79,702
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	1,498
Total short-term investments	108,828	31,036
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	117,770	16,400
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 short-term investments	50,437	12,416
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	25,519	8,173
Assets and liabilities measured at fair value on recurring basis | Fair Value | Agency bonds
Financial assets and liabilities measured at fair value on a recurring basis
Total short-term investments	7,482
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	30,582
Total short-term investments	6,239	5,233
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	1,497	1,001
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	$ 5,257	$ 5,196