Revenue (Schedule Of Revenue By Contract Type) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Contracts Revenue	$ 958,487	$ 1,028,156
Fixed Price [Member]
Contracts Revenue	512,490	510,329
Guaranteed Maximum Price [Member]
Contracts Revenue	212,970	282,679
Unit Price [Member]
Contracts Revenue	109,109	84,228
Cost Plus Fee And Other [Member]
Contracts Revenue	123,918	150,920
Civil [Member]
Contracts Revenue	333,494	263,114
Civil [Member] | Fixed Price [Member]
Contracts Revenue	242,867	183,904
Civil [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	2,233	5,072
Civil [Member] | Unit Price [Member]
Contracts Revenue	84,878	68,754
Civil [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	3,516	5,384
Building [Member]
Contracts Revenue	433,466	490,241
Building [Member] | Fixed Price [Member]
Contracts Revenue	114,359	79,001
Building [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	207,131	262,028
Building [Member] | Unit Price [Member]
Contracts Revenue	5,228	8,816
Building [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	106,748	140,396
Specialty Contractors [Member]
Contracts Revenue	191,527	274,801
Specialty Contractors [Member] | Fixed Price [Member]
Contracts Revenue	155,264	247,424
Specialty Contractors [Member] | Guaranteed Maximum Price [Member]
Contracts Revenue	3,606	15,579
Specialty Contractors [Member] | Unit Price [Member]
Contracts Revenue	19,003	6,658
Specialty Contractors [Member] | Cost Plus Fee And Other [Member]
Contracts Revenue	13,654	5,140
State And Local Agencies [Member]
Contracts Revenue	498,864	448,657
State And Local Agencies [Member] | Civil [Member]
Contracts Revenue	257,107	226,351
State And Local Agencies [Member] | Building [Member]
Contracts Revenue	144,686	115,986
State And Local Agencies [Member] | Specialty Contractors [Member]
Contracts Revenue	97,071	106,320
Federal Agencies [Member]
Contracts Revenue	71,078	72,889
Federal Agencies [Member] | Civil [Member]
Contracts Revenue	23,158	9,855
Federal Agencies [Member] | Building [Member]
Contracts Revenue	40,151	44,311
Federal Agencies [Member] | Specialty Contractors [Member]
Contracts Revenue	7,769	18,723
Private Owners [Member]
Contracts Revenue	388,545	506,610
Private Owners [Member] | Civil [Member]
Contracts Revenue	53,229	26,908
Private Owners [Member] | Building [Member]
Contracts Revenue	248,629	329,944
Private Owners [Member] | Specialty Contractors [Member]
Contracts Revenue	$ 86,687	$ 149,758