Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 1,177,725	$ 1,189,345	$ 1,125,275	$ 958,487	$ 1,183,284	$ 1,123,137	$ 1,120,085	$ 1,028,156	$ 4,450,832	$ 4,454,662	$ 4,757,208
Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									2,646,436	2,289,753
Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									780,352	1,117,934
Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									539,881	534,335
Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									484,163	512,640
Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,779,352	1,586,093	1,602,175
Civil [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,315,195	1,054,473
Civil [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									6,951	15,709
Civil [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									436,015	469,305
Civil [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									21,191	46,606
Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									1,742,040	1,861,699	1,941,325
Building [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									561,831	377,538
Building [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									752,110	1,040,093
Building [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									12,063	32,468
Building [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									416,036	411,600
Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									929,440	1,006,870	$ 1,213,708
Specialty Contractors [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									769,410	857,742
Specialty Contractors [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									21,291	62,132
Specialty Contractors [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									91,803	32,562
Specialty Contractors [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue									$ 46,936	$ 54,434