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Employee Retirement Benefit Plan	12 Months Ended
Employee Retirement Benefit Plan	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Retirement Benefit Plan	EMPLOYEE RETIREMENT BENEFIT PLAN We maintain a 401(k) defined contribution retirement plan for our eligible U.S. employees. Costs charged to operations in connection with the 401(k) plan during 2017, 2016, and 2015 aggregated $1.7 million, $1.4 million, and $1.3 million, respectively.