Fair Value Measurements (Details) $ in Millions | Sep. 30, 2019USD ($) |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | $ 141.5 |
Corporate bonds | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 51.2 |
U.S. treasury securities | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 29.8 |
Certificates of deposit | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 4.6 |
Recurring | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cost-method investments | 0.6 |
Total assets | 142.1 |
Recurring | Corporate bonds | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 51.2 |
Recurring | U.S. treasury securities | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 29.8 |
Recurring | Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 14.9 |
Recurring | Certificates of deposit | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 4.6 |
Recurring | Commercial paper | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 41.1 |
Recurring | Level 1 | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cost-method investments | 0 |
Total assets | 141.5 |
Recurring | Level 1 | Corporate bonds | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 51.2 |
Recurring | Level 1 | U.S. treasury securities | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 29.8 |
Recurring | Level 1 | Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 14.9 |
Recurring | Level 1 | Certificates of deposit | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 4.6 |
Recurring | Level 1 | Commercial paper | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 41.1 |
Recurring | Level 2 | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cost-method investments | 0 |
Total assets | 0 |
Recurring | Level 2 | Corporate bonds | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 2 | U.S. treasury securities | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 2 | Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 2 | Certificates of deposit | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 2 | Commercial paper | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 3 | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cost-method investments | 0.6 |
Total assets | 0.6 |
Recurring | Level 3 | Corporate bonds | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 3 | U.S. treasury securities | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 3 | Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 3 | Certificates of deposit | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | 0 |
Recurring | Level 3 | Commercial paper | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |
Cash equivalents and marketable securities | $ 0 |