Annual report pursuant to Section 13 and 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)

v3.19.3.a.u2
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
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents $ 824,876 $ 872,237 $ 736,431 $ 718,536
Short-Term Investments 112,037 100,029    
Long-Term Investments 94,589 93,745    
Adjusted Cost 1,031,502 1,066,011    
Fair Value 1,031,502 1,066,011    
Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 162,521 158,613    
Short-Term Investments 1,679 4,979    
Long-Term Investments 8,007 1,976    
Adjusted Cost 172,207 165,568    
Fair Value 172,207 165,568    
Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 110,358 95,050    
Long-Term Investments 86,582 91,769    
Adjusted Cost 196,940 186,819    
Fair Value 196,940 186,819    
Money market funds [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 162,521 158,613    
Adjusted Cost 162,521 158,613    
Fair Value 162,521 158,613    
U.S. Treasury Securities | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 1,679 4,979    
Long-Term Investments 8,007 1,976    
Adjusted Cost 9,686 6,955    
Fair Value 9,686 6,955    
Mutual Funds [Member] | Level 1 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Long-Term Investments 28,543 20,957    
Adjusted Cost 28,543 20,957    
Fair Value 28,543 20,957    
Corporate Notes and Bonds [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 104,130 88,412    
Long-Term Investments 28,301 43,868    
Adjusted Cost 132,431 132,280    
Fair Value 132,431 132,280    
Asset-backed Securities [Member] | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 263 2,115    
Long-Term Investments 23,351 21,195    
Adjusted Cost 23,614 23,310    
Fair Value 23,614 23,310    
U.S. Agency Securities | Level 2 [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Short-Term Investments 5,965 4,523    
Long-Term Investments 6,387 5,749    
Adjusted Cost 12,352 10,272    
Fair Value 12,352 10,272    
Cash [Member]        
Cash Cash Equivalents Short Term And Long Term Investments [Line Items]        
Cash and cash equivalents 662,355 713,624    
Fair Value $ 662,355 $ 713,624