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)

v3.20.2
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, 2020
Dec. 31, 2019
Jun. 30, 2019
Dec. 31, 2018
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents $ 1,352,120 $ 824,876 $ 779,281 $ 872,237
Short-Term Investments 105,677 112,037    
Long-Term Investments 98,236 94,589    
Adjusted Cost 1,556,033 1,031,502    
Fair Value 1,556,033 1,031,502    
Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 319,045 162,521    
Short-Term Investments 4,156 1,679    
Long-Term Investments 14,178 8,007    
Adjusted Cost 337,379 172,207    
Fair Value 337,379 172,207    
Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 101,521 110,358    
Long-Term Investments 84,058 86,582    
Adjusted Cost 185,579 196,940    
Fair Value 185,579 196,940    
Money market funds [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 319,045 162,521    
Adjusted Cost 319,045 162,521    
Fair Value 319,045 162,521    
U.S. Treasury Securities | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 4,156 1,679    
Long-Term Investments 14,178 8,007    
Adjusted Cost 18,334 9,686    
Fair Value 18,334 9,686    
Mutual Funds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Long-Term Investments 29,968 28,543    
Adjusted Cost 29,968 28,543    
Fair Value 29,968 28,543    
Corporate Notes and Bonds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 89,976 104,130    
Long-Term Investments 23,502 28,301    
Adjusted Cost 113,478 132,431    
Fair Value 113,478 132,431    
Asset-backed Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 4,696 263    
Long-Term Investments 29,787 23,351    
Adjusted Cost 34,483 23,614    
Fair Value 34,483 23,614    
U.S. Agency Securities | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 6,849 5,965    
Long-Term Investments 801 6,387    
Adjusted Cost 7,650 12,352    
Fair Value 7,650 12,352    
Cash [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 1,033,075 662,355    
Fair Value $ 1,033,075 $ 662,355