Short-term Investments - Additional Information (Details)
$ in Millions
Dec. 31, 2018
|Investments Debt And Equity Securities [Abstract]|
|Held-to-maturity investments with contractual maturities less than one year||$ 32.7|
Amount of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef