Summary of Significant Accounting Policies and Basis of Presentation - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 13,973	$ 18,823	$ 15,723	$ 15,122
Short-term investments	1,400	$ 1,900
United States
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	5,700
Canada
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	1,200
Other
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 7,100