Revenue Recognition (Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Revenue Recognition [Abstract]
Contract Assets, Current		$ 36,500	$ 21,912
Contract Assets, Non-Current	[1]	12,065	54,232
Contract Liabilities, Current		2,988	2,896
Contract Liabilities, Non-Current		$ 19,834	$ 23,170

[1] See Revenue Recognition (Note 3) for discussion on the circumstances that result in the recognition of contract assets.