Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Accounting Policies Revenue Recognition (Details)

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Basis of Presentation and Accounting Policies Revenue Recognition (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Revenue Recognition and Deferred Revenue [Abstract]    
Contract with Customer, Liability $ 7,051 $ 983
Deferred Revenue, Additions 6,483  
Contract with Customer, Liability, Revenue Recognized $ (415)