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Retirement Plans	12 Months Ended
Retirement Plans	Dec. 31, 2017
Postemployment Benefits [Abstract]
Retirement Plans	Retirement Plans We have a 401(k) retirement and savings plan made available to all United States employees. The 401(k) plan allows each participant to contribute up to an amount not to exceed an annual statutory maximum. We began contributing to the 401(k) plan in 2017. For the year ended December 31, 2017, we made matching contributions of $1.1 million.