Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 1,183,284	$ 1,123,137	$ 1,120,085	$ 1,028,156	$ 1,193,068	$ 1,199,505	$ 1,247,274	$ 1,117,361	$ 4,454,662	$ 4,757,208	$ 4,973,076
Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									2,289,753
Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,117,934
Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									534,335
Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									512,640
Civil
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,586,093	1,602,175	1,668,963
Civil | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,054,473
Civil | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									15,709
Civil | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									469,305
Civil | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									46,606
Building
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,861,699	1,941,325	2,069,841
Building | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									377,538
Building | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,040,093
Building | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									32,468
Building | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									411,600
Specialty Contractors
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,006,870	$ 1,213,708	$ 1,234,272
Specialty Contractors | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									857,742
Specialty Contractors | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									62,132
Specialty Contractors | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									32,562
Specialty Contractors | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									$ 54,434