Segment Information (Dredging Revenue By Type Of Work) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	$ 856,878	$ 806,831	$ 731,418
Dredging [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	681,255	697,711	642,602
Dredging [Member] | Capital Dredging - U.S. [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	207,058	195,635	153,781
Dredging [Member] | Capital dredging - Foreign [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	139,945	155,000	138,436
Dredging [Member] | Beach Nourishment Dredging [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	184,060	194,219	228,868
Dredging [Member] | Maintenance Dredging [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	120,055	123,923	90,833
Dredging [Member] | Rivers & Lakes [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue as reported	$ 30,137	$ 28,934	$ 30,684