General - Accounts Receivable, Contract Assets and Contract Liabilities - Tabular Disclosure (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies
Accounts receivable	$ 822,354	$ 717,455
Change in accounts receivable	$ 104,899
Change in accounts receivable (as a percent)	14.60%
Contract assets	$ 12,419	2,162
Change in contract assets	$ (10,257)
Change in contract assets (as a percent)	474.40%
Contract liabilities - current	$ 12,071	6,728
Change in contract liabilities - current	$ 5,343
Change in contract liabilities - current (as a percent)	79.40%
Contract liabilities - long-term	$ 11,480	$ 11,099
Change in contract liabilities - long-term	$ 381
Change in contract liabilities - long-term (as a percent)	3.40%