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Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2017
Text Block [Abstract]
Defined Contribution Plan Disclosure [Text Block]	9. Employee Benefit Plan Defined Contribution Plan The Company sponsors a 401(k) plan for all eligible employees. The plan allows participants to contribute up to $18,000 in 2017, tax deferred (subject to IRS guidelines). The plan also allows discretionary Company contributions as determined by the Company’s Board of Directors. Effective January 1, 2006, the Company implemented a discretionary match of up to two percent of participating employee contributions. The employer contribution will vest 20% after two years and 20% each additional year until it is fully vested in year six. Contribution expense to the Company was $7.9 million, $6.3 million and $5.4 million in the years ended December 31, 2017, 2016 and 2015, respectively.