Revisions in Estimates (Tables)

12 Months Ended

Dec. 31, 2017

Construction [Member]

Change in Accounting Estimate [Line Items]

Schedule of Change in Accounting Estimate

Increases

Years Ended December 31,		2017		2016		2015
Number of projects with upward estimate changes		10		7		14
Range of increase in gross profit from each project, net	$	1.1 - 3.9	$	1.1 - 4.8	$	1.1 - 6.6
Increase on project profitability	$	17.2	$	14.2	$	30.7

Decreases

Years Ended December 31,		2017		2016		2015
Number of projects with downward estimate changes		6		7		5
Range of reduction in gross profit from each project, net	$	1.0 - 4.4	$	1.0 - 3.9	$	1.0 - 3.3
Decrease on project profitability	$	13.2	$	12.9	$	10.8

Large Project Construction [Member]

Change in Accounting Estimate [Line Items]

Schedule of Change in Accounting Estimate

Decreases

Years Ended December 31,		2017		2016		2015
Number of projects with downward estimate changes		7		5		6
Range of reduction in gross profit from each project, net	$	1.3 - 17.2	$	1.3 - 13.6	$	1.0 - 5.5
Decrease on project profitability	$	68.6	$	40.7	$	20.3

Increases

Years Ended December 31,		2017		2016		2015
Number of projects with upward estimate changes		1		8		7
Range of increase in gross profit from each project, net	$	2.0	$	1.2 - 6.5	$	1.5 - 6.7
Increase on project profitability	$	2.0	$	27.2	$	27.9