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
Jun. 30, 2021
Dec. 31, 2020
Jun. 30, 2020
Dec. 31, 2019
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents $ 1,091,355 $ 1,370,826 $ 1,352,120 $ 824,876
Short-Term Investments 107,626 100,767    
Long-Term Investments 122,542 108,412    
Adjusted Cost 1,321,523 1,580,005    
Fair Value 1,321,523 1,580,005    
Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 260,556 423,865    
Short-Term Investments 7,967 8,067    
Long-Term Investments 11,676 13,079    
Adjusted Cost 280,199 445,011    
Fair Value 280,199 445,011    
Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 99,659 92,700    
Long-Term Investments 110,866 95,333    
Adjusted Cost 210,525 188,033    
Fair Value 210,525 188,033    
Money market funds [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 260,556 423,865    
Adjusted Cost 260,556 423,865    
Fair Value 260,556 423,865    
U.S. Treasury Securities [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 7,967 8,067    
Long-Term Investments 11,676 13,079    
Adjusted Cost 19,643 21,146    
Fair Value 19,643 21,146    
Corporate Notes and Bonds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 94,363 83,521    
Long-Term Investments 43,894 33,732    
Adjusted Cost 138,257 117,253    
Fair Value 138,257 117,253    
Asset-backed Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 4,698 5,498    
Long-Term Investments 21,733 22,755    
Adjusted Cost 26,431 28,253    
Fair Value 26,431 28,253    
U.S. Agency Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 598 3,681    
Long-Term Investments 0 0    
Adjusted Cost 598 3,681    
Fair Value 598 3,681    
Mutual Funds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 0 0    
Long-Term Investments 45,239 38,846    
Adjusted Cost 45,239 38,846    
Fair Value 45,239 38,846    
Cash [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 830,799 946,961    
Fair Value $ 830,799 $ 946,961