Consolidated Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
(Increase) decrease in:
Accounts and notes receivable, net	$ 162,655	$ (337,775)	$ 190,141
Contract work in progress	140,556	(72,419)	80,742
Other current assets	(138,638)	19,311	(20,861)
Other assets	(3,944)	250,332	(54,726)
Increase (decrease) in:
Trade accounts payable	(137,441)	200,480	(57,317)
Advance billings on contracts	60,808	43,985	243,996
Accrued liabilities	(65,207)	40,088	(38,529)
Other liabilities	(30,688)	(8,609)	(39,550)
Increase (decrease) in cash due to changes in operating assets and liabilities	(11,899)	135,393	303,896
Cash paid during the year for:
Interest	61,560	72,057	40,585
Income taxes (net of refunds)	$ 175,045	$ 164,836	$ 249,921

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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