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401(k) plan (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract] |  |  |
Matching contribution up to the first 6% of employee's base salary (as a percent) | 50.00% |  |
Percentage of employee's base salary, matched by employer | 6.00% |  |
Expense recorded | $ 1.1 | $ 0.7 | $ 0.3

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- References No definition available. + Details
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- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
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