General - Accounts Receivable, Contract Assets and Contract Liabilities - Tabular Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies
Accounts receivable	$ 961,441	$ 915,656
Change in accounts receivable	$ 45,785
Change in accounts receivable (as a percent)	5.00%
Contract assets	$ 12,333	2,231
Change in contract assets	$ (10,102)
Change in contract assets (as a percent)	452.80%
Contract liabilities - current	$ 38,687	6,728
Change in contract liabilities - current	$ 31,959
Change in contract liabilities - current (as a percent)	475.00%
Contract liabilities - long-term	$ 10,895	$ 11,099
Change in contract liabilities - long-term	$ (204)
Change in contract liabilities - long-term (as a percent)	(1.80%)