Accounts Receivable, Accounts Payable and Accrued Liabilities (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Accounts Receivable, Net [Abstract]
Receivables from contracts with customers, less doubtful accounts	$ 538,021	$ 600,215
Other receivables	44,259	20,104
Accounts receivable, net	582,280	620,319		$ 622,461
Allowance for Doubtful Accounts Receivable	14,775	22,975
Accounts Payable, Current [Abstract]
Accounts payable and accrued liabilities	337,123	385,927
Accrued compensation and related benefits	149,455	140,396
Total accounts payable and accrued liabilities	486,578	526,323		$ 526,411
Allowance for doubtful accounts[Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	22,975	26,723	$ 27,854
Additions - Charged to Costs and Expenses	10,209	33,830	29,718
Deductions	(18,409)	(37,578)	(30,849)
Balance at End of Period	$ 14,775	$ 22,975	$ 26,723