Revenues (Schedule of Contract with Customer, Assets and Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Contract Liabilities
Beginning balance	$ 360,416	$ 246,010
Consideration earned during the period	(43,967)	(17,885)
Consideration received during the period	61,221	64,432
Ending balance	$ 377,670	$ 292,557