Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018
Assets:
Money market instruments	$ 16,081	$ 3,557
Financial assets at fair value	796,713
Corporate Bonds
Assets:
Financial assets at fair value	255,207
Treasury Bills
Assets:
Financial assets at fair value	362,069
Asset-Backed Securities
Assets:
Financial assets at fair value	146,392
Sovereign Bonds
Assets:
Financial assets at fair value	22,300
Agency Bonds
Assets:
Financial assets at fair value	5,905
Municipal Bonds
Assets:
Financial assets at fair value	4,840
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets:
Money market instruments	16,081
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets:
Money market instruments	0
Economic hedge forward contracts	19
Liabilities:
Economic hedge forward contracts	70
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate Bonds
Assets:
Financial assets at fair value	255,207
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Treasury Bills
Assets:
Financial assets at fair value	362,069
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Asset-Backed Securities
Assets:
Financial assets at fair value	146,392
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Sovereign Bonds
Assets:
Financial assets at fair value	22,300
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Agency Bonds
Assets:
Financial assets at fair value	5,905
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Municipal Bonds
Assets:
Financial assets at fair value	4,840
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Liabilities:
Contingent consideration liabilities	$ 1,153