6. Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2016	Dec. 31, 2017
Goodwill And Intangible Assets - Goodwill Details
Goodwill	$ 12,100	$ 30,600	$ 12,100
Goodwill impairment	$ 0	$ (18,500)

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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