Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.10.0.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities $ 9,980 $ 39,844
Money market funds    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 46,386 17,205
Overnight repurchase agreements    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 68,000 15,000
Recurring    
Assets measured at fair value on a recurring basis:    
Total 124,366 72,049
Recurring | U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities 9,980 39,844
Recurring | Money market funds    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 46,386 17,205
Recurring | Overnight repurchase agreements    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 68,000 15,000
Recurring | Level 1    
Assets measured at fair value on a recurring basis:    
Total 56,366 57,049
Recurring | Level 1 | U.S treasury obligations    
Assets measured at fair value on a recurring basis:    
Marketable securities 9,980 39,844
Recurring | Level 1 | Money market funds    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents 46,386 17,205
Recurring | Level 2    
Assets measured at fair value on a recurring basis:    
Total 68,000 15,000
Recurring | Level 2 | Overnight repurchase agreements    
Assets measured at fair value on a recurring basis:    
Cash and cash equivalents $ 68,000 $ 15,000