Fair Value Measurements - Information about Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Mar. 31, 2017 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | $ 171,689 | $ 170,437 |
Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 55,688 | 44,221 |
Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 107,799 | 118,101 |
Restricted cash: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 8,202 | 8,115 |
Money market funds | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 42,280 | 36,180 |
Commercial paper | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 6,486 | 5,441 |
Commercial paper | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 12,648 | 10,549 |
Certificates of deposit | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 25,601 | 28,210 |
Corporate notes and bonds | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 15,837 | 17,378 |
U.S. treasury securities | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 2,997 | |
U.S. treasury securities | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 18,937 | 11,276 |
U.S. government agencies | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 3,925 | 2,600 |
U.S. government agencies | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 34,776 | 50,688 |
Money market funds | Restricted cash: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 8,202 | 8,115 |
Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 72,416 | 55,571 |
Level 1 | Money market funds | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 42,280 | 36,180 |
Level 1 | Commercial paper | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | Commercial paper | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | Certificates of deposit | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | Corporate notes and bonds | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | U.S. treasury securities | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 2,997 | |
Level 1 | U.S. treasury securities | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 18,937 | 11,276 |
Level 1 | U.S. government agencies | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | U.S. government agencies | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 1 | Money market funds | Restricted cash: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 8,202 | 8,115 |
Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 99,273 | 114,866 |
Level 2 | Money market funds | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 2 | Commercial paper | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 6,486 | 5,441 |
Level 2 | Commercial paper | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 12,648 | 10,549 |
Level 2 | Certificates of deposit | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 25,601 | 28,210 |
Level 2 | Corporate notes and bonds | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 15,837 | 17,378 |
Level 2 | U.S. treasury securities | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | |
Level 2 | U.S. treasury securities | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 2 | U.S. government agencies | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 3,925 | 2,600 |
Level 2 | U.S. government agencies | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 34,776 | 50,688 |
Level 2 | Money market funds | Restricted cash: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Money market funds | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Commercial paper | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Commercial paper | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Certificates of deposit | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Corporate notes and bonds | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | U.S. treasury securities | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | |
Level 3 | U.S. treasury securities | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | U.S. government agencies | Cash and cash equivalents: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | U.S. government agencies | Short-term investments: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | 0 | 0 |
Level 3 | Money market funds | Restricted cash: | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets fair value | $ 0 | $ 0 |