Accounts Receivable, Accounts Payable and Accrued Liabilities (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Accounts Receivable, after Allowance for Credit Loss [Abstract]
Receivables from contracts with customers, less doubtful accounts	$ 595,321	$ 538,021
Other receivables	28,895	44,259
Accounts receivable, net	624,216	582,280
Accounts Receivable, Allowance for Credit Loss	14,276	14,775
Accounts Payable, Current [Abstract]
Accounts payable and accrued liabilities	366,963	337,123
Accrued compensation and related benefits	140,738	149,455
Total accounts payable and accrued liabilities	507,701	486,578		$ 472,549
Allowance for doubtful accounts[Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	14,775	22,975	$ 26,723
Additions - Charged to Costs and Expenses	1,706	10,209	33,830
Deductions	(2,205)	(18,409)	(37,578)
Balance at End of Period	$ 14,276	$ 14,775	$ 22,975