Investments (Detail) - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
---|---|---|
Schedule Of Investments [Line Items] | ||
Investments | $ 48,915 | |
Investments | 757,233 | $ 725,227 |
Commercial paper | ||
Schedule Of Investments [Line Items] | ||
Investments | 135,197 | 94,572 |
Corporate debt securities | ||
Schedule Of Investments [Line Items] | ||
Investments | 414,951 | 544,978 |
Securities of government-sponsored entities | ||
Schedule Of Investments [Line Items] | ||
Investments | 158,170 | $ 85,677 |
Restricted equity securities | ||
Schedule Of Investments [Line Items] | ||
Investments | $ 48,915 |