Contract Assets and Liabilities Changes in Net Contract Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Contract assets
Contract asset, current	$ 2,183	$ 1,145
Contract asset, non-current	244	188
Contract asset	2,427	1,333
Contract Liabilities
Contract liability, current	4,473	5,963
Contract liability, non-current	383	1,401
Contract liabilities	$ 4,856	$ 7,364