Revenue (Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Contracts Revenue	$ 1,028,156	$ 1,117,361
State And Local Agencies [Member]
Contracts Revenue	448,657
Federal Agencies [Member]
Contracts Revenue	72,889
Private Owners [Member]
Contracts Revenue	506,610
Civil [Member]
Contracts Revenue	263,114	304,575
Civil [Member] \| State And Local Agencies [Member]
Contracts Revenue	226,351
Civil [Member] \| Federal Agencies [Member]
Contracts Revenue	9,855
Civil [Member] \| Private Owners [Member]
Contracts Revenue	26,908
Civil [Member] \| Mass Transit [Member]
Contracts Revenue	150,126
Civil [Member] \| Bridges [Member]
Contracts Revenue	62,811
Civil [Member] \| Highways [Member]
Contracts Revenue	17,257
Civil [Member] \| Other [Member]
Contracts Revenue	32,920
Building [Member]
Contracts Revenue	490,241	497,090
Building [Member] \| State And Local Agencies [Member]
Contracts Revenue	115,986
Building [Member] \| Federal Agencies [Member]
Contracts Revenue	44,311
Building [Member] \| Private Owners [Member]
Contracts Revenue	329,944
Building [Member] \| Office [Member]
Contracts Revenue	147,322
Building [Member] \| Hospitality And Gaming [Member]
Contracts Revenue	81,765
Building [Member] \| Health Care Facilities [Member]
Contracts Revenue	75,081
Building [Member] \| Municipal And Government [Member]
Contracts Revenue	50,452
Building [Member] \| Mixed Use [Member]
Contracts Revenue	41,777
Building [Member] \| Education Facilities [Member]
Contracts Revenue	32,482
Building [Member] \| Industrial And Commercial [Member]
Contracts Revenue	26,425
Building [Member] \| Other [Member]
Contracts Revenue	34,937
Specialty Contractors [Member]
Contracts Revenue	274,801	$ 315,696
Specialty Contractors [Member] \| State And Local Agencies [Member]
Contracts Revenue	106,320
Specialty Contractors [Member] \| Federal Agencies [Member]
Contracts Revenue	18,723
Specialty Contractors [Member] \| Private Owners [Member]
Contracts Revenue	149,758
Specialty Contractors [Member] \| Mass Transit [Member]
Contracts Revenue	75,182
Specialty Contractors [Member] \| Health Care Facilities [Member]
Contracts Revenue	16,365
Specialty Contractors [Member] \| Mixed Use [Member]
Contracts Revenue	47,857
Specialty Contractors [Member] \| Education Facilities [Member]
Contracts Revenue	25,304
Specialty Contractors [Member] \| Industrial And Commercial [Member]
Contracts Revenue	39,339
Specialty Contractors [Member] \| Transportation [Member]
Contracts Revenue	33,985
Specialty Contractors [Member] \| Condominiums [Member]
Contracts Revenue	23,089
Specialty Contractors [Member] \| Other [Member]
Contracts Revenue	$ 13,680