Revenue (Disaggregation Of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Contracts Revenue	$ 1,120,085	$ 1,247,274	$ 2,148,241	$ 2,364,635
State And Local Agencies [Member]
Contracts Revenue	593,059		1,041,715
Federal Agencies [Member]
Contracts Revenue	98,023		170,913
Private Owners [Member]
Contracts Revenue	429,003		935,613
Civil [Member]
Contracts Revenue	402,473	472,582	665,587	777,157
Civil [Member] \| State And Local Agencies [Member]
Contracts Revenue	327,195		553,546
Civil [Member] \| Federal Agencies [Member]
Contracts Revenue	30,772		40,627
Civil [Member] \| Private Owners [Member]
Contracts Revenue	44,506		71,414
Civil [Member] \| Mass Transit [Member]
Contracts Revenue	158,096		308,222
Civil [Member] \| Bridges [Member]
Contracts Revenue	120,929		183,739
Civil [Member] \| Highways [Member]
Contracts Revenue	65,809		83,066
Civil [Member] \| Tunneling [Member]
Contracts Revenue	23,931		32,632
Civil [Member] \| Other [Member]
Contracts Revenue	33,708		57,928
Building [Member]
Contracts Revenue	446,979	492,835	937,220	989,925
Building [Member] \| State And Local Agencies [Member]
Contracts Revenue	159,556		275,541
Building [Member] \| Federal Agencies [Member]
Contracts Revenue	52,263		96,574
Building [Member] \| Private Owners [Member]
Contracts Revenue	235,160		565,105
Building [Member] \| Health Care Facilities [Member]
Contracts Revenue	118,116		193,197
Building [Member] \| Office [Member]
Contracts Revenue	39,237		186,559
Building [Member] \| Hospitality And Gaming [Member]
Contracts Revenue	79,490		161,255
Building [Member] \| Municipal And Government [Member]
Contracts Revenue	70,528		120,981
Building [Member] \| Mixed Use [Member]
Contracts Revenue	38,814		80,590
Building [Member] \| Education Facilities [Member]
Contracts Revenue	32,876		65,358
Building [Member] \| Industrial And Commercial [Member]
Contracts Revenue	20,081		46,507
Building [Member] \| Other [Member]
Contracts Revenue	47,837		82,773
Specialty Contractors [Member]
Contracts Revenue	270,633	$ 281,857	545,434	$ 597,553
Specialty Contractors [Member] \| State And Local Agencies [Member]
Contracts Revenue	106,308		212,628
Specialty Contractors [Member] \| Federal Agencies [Member]
Contracts Revenue	14,988		33,712
Specialty Contractors [Member] \| Private Owners [Member]
Contracts Revenue	149,337		299,094
Specialty Contractors [Member] \| Mass Transit [Member]
Contracts Revenue	78,169		153,351
Specialty Contractors [Member] \| Health Care Facilities [Member]
Contracts Revenue	14,623		30,988
Specialty Contractors [Member] \| Mixed Use [Member]
Contracts Revenue	51,976		99,833
Specialty Contractors [Member] \| Education Facilities [Member]
Contracts Revenue	26,298		51,602
Specialty Contractors [Member] \| Industrial And Commercial [Member]
Contracts Revenue	36,540		75,878
Specialty Contractors [Member] \| Transportation [Member]
Contracts Revenue	22,019		56,004
Specialty Contractors [Member] \| Condominiums [Member]
Contracts Revenue	22,761		45,850
Specialty Contractors [Member] \| Other [Member]
Contracts Revenue	$ 18,247		$ 31,928