Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 927,172	$ 1,473,905
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	611,946	855,795
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	252,158	282,840
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	44,218	133,186
Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	10,726	10,726
Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	4,824	167,342
Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	2,741
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	559	586
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,587,658	1,903,748
Derivative assets	12	389
Total	1,587,670	1,904,137
Contingent consideration	15,581	45,102
Derivative liabilities	224	446
Total	15,805	45,548
Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	155,543	197,955
Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	482,330	231,888
Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	611,946
Available for sale securities		855,795
Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	252,158
Available for sale securities		282,840
Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	44,218
Available for sale securities		133,186
Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	10,726
Available for sale securities		10,726
Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	4,824
Available for sale securities		167,342
Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	2,741
Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	559
Available for sale securities		586
Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	22,613
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	487,607	427,720
Total	487,607	427,720
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	155,543	197,955
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	306,710	206,335
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity and Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities		23,430
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	2,741
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Fair Value, Measurements, Recurring | Equity Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale equity securities	22,613
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	1,100,051	1,476,028
Derivative assets	12	389
Total	1,100,063	1,476,417
Derivative liabilities	224	446
Total	224	446
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and cash equivalents	175,620	25,553
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	611,946
Available for sale securities		855,795
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	252,158
Available for sale securities		282,840
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	44,218
Available for sale securities		133,186
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	10,726
Available for sale securities		10,726
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Certificates of Deposit and Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	4,824
Available for sale securities		167,342
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale debt securities	559
Available for sale securities		586
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration	15,581	45,102
Total	$ 15,581	$ 45,102