Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 1,125,275	$ 1,120,085	$ 2,083,762	$ 2,148,241
Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	674,021	591,079	1,186,510	1,101,407
Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	194,009	291,005	406,981	573,685
Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	139,268	139,451	248,377	223,679
Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	117,977	98,550	241,894	249,470
Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	473,658	402,473	807,152	665,587
Civil [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	349,945	259,927	592,811	443,830
Civil [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	1,644	3,103	3,878	8,175
Civil [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	116,285	121,447	201,163	190,201
Civil [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	5,784	17,996	9,300	23,381
Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	428,318	446,979	861,784	937,220
Building [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	136,250	96,657	250,609	175,658
Building [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	185,050	270,440	392,182	532,468
Building [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	2,800	10,771	8,028	19,588
Building [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	104,218	69,111	210,965	209,506
Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	223,299	270,633	414,826	545,434
Specialty Contractors [Member] | Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	187,826	234,495	343,090	481,919
Specialty Contractors [Member] | Guaranteed Maximum Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	7,315	17,462	10,921	33,042
Specialty Contractors [Member] | Unit Price [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	20,183	7,233	39,186	13,890
Specialty Contractors [Member] | Cost Plus Fee And Other [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	7,975	11,443	21,629	16,583
State And Local Agencies [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	629,491	593,059	1,128,355	1,041,715
State And Local Agencies [Member] | Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	381,438	327,195	638,545	553,546
State And Local Agencies [Member] | Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	133,798	159,556	278,484	275,541
State And Local Agencies [Member] | Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	114,255	106,308	211,326	212,628
Private Owners [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	421,648	429,003	810,193	935,613
Private Owners [Member] | Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	65,241	44,506	118,470	71,414
Private Owners [Member] | Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	250,124	235,160	498,753	565,105
Private Owners [Member] | Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	106,283	149,337	192,970	299,094
Federal Agencies [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	74,136	98,023	145,214	170,913
Federal Agencies [Member] | Civil [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	26,979	30,772	50,137	40,627
Federal Agencies [Member] | Building [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	44,396	52,263	84,547	96,574
Federal Agencies [Member] | Specialty Contractors [Member]
Disaggregation of Revenue [Line Items]
Contracts Revenue	$ 2,761	$ 14,988	$ 10,530	$ 33,712