XML 53 R43.htm IDEA: XBRL DOCUMENT v3.21.1
Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted and restricted cash equivalents and investments $ 3,260,826 $ 3,284,061
Fair Value Measurements on a Recurring Basis    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 1,373,721 1,342,085
Total restricted cash equivalents and investments 1,060,558 1,159,963
Total unrestricted and restricted cash equivalents and investments 2,434,279 2,502,048
Fair Value Measurements on a Recurring Basis | Level 1    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 88,630 0
Total restricted cash equivalents and investments 126,649 24,757
Total unrestricted and restricted cash equivalents and investments 215,279 24,757
Fair Value Measurements on a Recurring Basis | Level 2    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 1,285,091 1,342,085
Total restricted cash equivalents and investments 933,909 1,135,206
Total unrestricted and restricted cash equivalents and investments 2,219,000 2,477,291
Fair Value Measurements on a Recurring Basis | Level 3    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Total unrestricted and restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Money market funds    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 88,630  
Total restricted cash equivalents and investments 126,649 24,757
Fair Value Measurements on a Recurring Basis | Money market funds | Level 1    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 88,630  
Total restricted cash equivalents and investments 126,649 24,757
Fair Value Measurements on a Recurring Basis | Money market funds | Level 2    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0  
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Money market funds | Level 3    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0  
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Certificates of deposit    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 864,598 677,777
Total restricted cash equivalents and investments 606,331 481,365
Fair Value Measurements on a Recurring Basis | Certificates of deposit | Level 1    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Certificates of deposit | Level 2    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 864,598 677,777
Total restricted cash equivalents and investments 606,331 481,365
Fair Value Measurements on a Recurring Basis | Certificates of deposit | Level 3    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Commercial paper    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 312,873 376,789
Total restricted cash equivalents and investments 258,637 469,240
Fair Value Measurements on a Recurring Basis | Commercial paper | Level 1    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Commercial paper | Level 2    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 312,873 376,789
Total restricted cash equivalents and investments 258,637 469,240
Fair Value Measurements on a Recurring Basis | Commercial paper | Level 3    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Corporate bonds    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 107,620 287,519
Total restricted cash equivalents and investments 68,941 184,601
Fair Value Measurements on a Recurring Basis | Corporate bonds | Level 1    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments 0 0
Fair Value Measurements on a Recurring Basis | Corporate bonds | Level 2    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 107,620 287,519
Total restricted cash equivalents and investments 68,941 184,601
Fair Value Measurements on a Recurring Basis | Corporate bonds | Level 3    
Financial Instruments Measured at Fair Value on a Recurring Basis    
Total unrestricted cash equivalents and investments 0 0
Total restricted cash equivalents and investments $ 0 $ 0