Summary of Significant Accounting Policies and Other Items - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies and Other Items
Balance at Beginning of Period	$ 7,310	$ 5,885	$ 4,770
Expense (recovery)	2,552	1,451	1,259
Write off	(90)		(103)
Other		(26)	(41)
Balance at End of Period	$ 9,772	$ 7,310	$ 5,885