Quarterly report pursuant to Section 13 or 15(d)

Cash, Cash Equivalents, Short-Term and Long-Term Investments - Summary of Cash, Cash Equivalents, Short-Term and Long-Term Investments by Significant Investment Category (Detail)

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Cash, Cash Equivalents, Short-Term and Long-Term Investments - Summary of Cash, Cash Equivalents, Short-Term and Long-Term Investments by Significant Investment Category (Detail) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents $ 1,284,540 $ 1,370,826 $ 1,158,766 $ 824,876
Short-Term Investments 106,028 100,767    
Long-Term Investments 124,379 108,412    
Adjusted Cost 1,514,947 1,580,005    
Fair Value 1,514,947 1,580,005    
Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 417,919 423,865    
Short-Term Investments 8,362 8,067    
Long-Term Investments 14,189 13,079    
Adjusted Cost 440,470 445,011    
Fair Value 440,470 445,011    
Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 97,666 92,700    
Long-Term Investments 110,190 95,333    
Adjusted Cost 207,856 188,033    
Fair Value 207,856 188,033    
Money market funds [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 417,919 423,865    
Adjusted Cost 417,919 423,865    
Fair Value 417,919 423,865    
U.S. Treasury Securities [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 8,362 8,067    
Long-Term Investments 14,189 13,079    
Adjusted Cost 22,551 21,146    
Fair Value 22,551 21,146    
Corporate Notes and Bonds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 93,422 83,521    
Long-Term Investments 45,085 33,732    
Adjusted Cost 138,507 117,253    
Fair Value 138,507 117,253    
Asset-backed Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 2,257 5,498    
Long-Term Investments 23,574 22,755    
Adjusted Cost 25,831 28,253    
Fair Value 25,831 28,253    
U.S. Agency Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 1,987 3,681    
Adjusted Cost 1,987 3,681    
Fair Value 1,987 3,681    
Mutual Funds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Long-Term Investments 41,531 38,846    
Adjusted Cost 41,531 38,846    
Fair Value 41,531 38,846    
Cash [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 866,621 946,961    
Fair Value $ 866,621 $ 946,961