Segment Information (Details)	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2015 segment	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Contract revenues	$ 99,211,000	$ 125,073,000	$ 159,767,000	$ 136,843,000	$ 162,214,000	$ 140,162,000	$ 137,420,000	$ 138,757,000		$ 520,894,000	$ 578,553,000	$ 578,236,000
Number of reportable segments | segment									2	2
Intersegment Eliminations
Segment Reporting Information [Line Items]
Contract revenues										$ 2,500,000	0
Heavy Civil Marine Construction Segment
Segment Reporting Information [Line Items]
Contract revenues										243,883,000
Heavy Civil Marine Construction Segment | Mexico and the Caribbean
Segment Reporting Information [Line Items]
Contract revenues										$ 12,200,000	$ 9,400,000