Revenue (Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Receivables, including unbilled receivables presented in prepaid expenses and other current assets	$ 375,822	$ 333,044
Receivables, including unbilled receivables change	42,778
Contract assets	33,871	32,125
Contract assets change	1,746
Contract liabilities	42,610	$ 31,094
Contract liabilities change	$ 11,516