Prepaid Expenses and Other Current Assets and Accrued and Other Current Liabilities Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Other Current Assets And Other Current Liabilities [Abstract]
Payroll and related costs	$ 5,190	$ 8,106
Securities litigation expense payable	413	17,127
Operating lease liabilities	1,613	1,617
Other accrued and other current liabilities	4,636	5,138
Accrued and other current liabilities	$ 11,852	$ 31,988