Revenues (Schedule of Contract with Customer, Assets and Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Contract Liabilities
Beginning balance	$ 360,416	$ 246,010
Consideration earned during the period	(71,778)	(30,200)
Consideration received during the period	127,030	122,526
Ending balance	$ 415,668	$ 338,336