Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($) |
12 Months Ended | |||
|---|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Basis Of Presentation And Significant Accounting Policies [Line Items] | ||||
| Cash and cash equivalents | $ 43,471,000 | $ 25,742,000 | $ 65,767,000 | $ 78,445,000 |
| Impairment charges recognized | 200,000 | 200,000 | ||
| Unrecognized tax benefits, income tax penalties or interest charged | 0 | |||
| Allocation of undistributed earnings to participating securities | $ 3,279,000 | 0 | 0 | |
| Contractual obligation | $ 0 | $ 0 | ||
| Equipment [Member] | ||||
| Basis Of Presentation And Significant Accounting Policies [Line Items] | ||||
| Useful lives | 3 years | |||
| X | ||||||||||
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments. No definition available.
|
| X | ||||||||||
- Definition The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale). Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. No definition available.
|
| X | ||||||||||
- Definition Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Basis of presentation and significant accounting policies. No definition available.
|
| X | ||||||||||
- Details
|