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Company Retirement Plans (Details) - United States - 401(k) Plan - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Company retirement plans |  |  |
Employer discretionary contributions | $ 0 | $ 0 | $ 0
Employer's contribution | $ 4,600 | $ 4,200 | $ 4,000

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- References No definition available. + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Details
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