Revisions in Estimates (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in Accounting Estimate [Line Items]
Initial gross profit impact from projects exceeding threshold	$ 79,791,000	$ 66,692,000	$ 82,415,000	$ 21,408,000	$ 49,751,000	$ 55,860,000	$ 49,596,000	$ 30,058,000	$ 250,306,000	$ 185,263,000	$ 234,759,000
Financial Effect on Future Periods	0								0
Amount Considered Significant on Individual Project Gross Profit	1,000,000									1,000,000
Construction [Member]
Change in Accounting Estimate [Line Items]
Percent complete of contract with estimate change									56.80%
Construction Contract Backlog, Percent	2.40%								2.40%
Increase (Decrease) on Project Profitability									(7,300,000)	(1,700,000)	(18,100,000)
Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Total Contract Value	75,000,000								75,000,000
Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Total Contract Value	75,000,000								75,000,000
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability									(46,900,000)	(25,500,000)	(64,600,000)
Contracts Accounted for under Percentage of Completion [Member] | Large Project Construction [Member] | Noncontrolling Interest [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability									(9,500,000)	5,600,000	(3,100,000)
Upward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Initial gross profit impact from projects exceeding threshold									74,700,000	9,100,000	16,400,000
Increase (Decrease) on Project Profitability									(9,200,000)	(16,100,000)	(8,100,000)
Number of Projects with Estimate Changes									7	6	6
Upward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									1,000,000	1,100,000	1,000,000
Upward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									1,800,000	3,700,000	1,700,000
Upward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability									(66,800,000)	(77,500,000)	(92,000,000)
Number of Projects with Estimate Changes									12	7	10
Upward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									1,000,000	2,600,000	1,100,000
Upward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									15,200,000	41,300,000	24,500,000
Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability									16,500,000	17,800,000	26,200,000
Number of Projects with Estimate Changes									6	5	9
Downward Estimate Change [Member] | Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									(1,600,000)	(1,200,000)	(1,000,000)
Downward Estimate Change [Member] | Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									(4,100,000)	(7,400,000)	(6,600,000)
Downward Estimate Change [Member] | Large Project Construction [Member]
Change in Accounting Estimate [Line Items]
Increase (Decrease) on Project Profitability									19,900,000	52,000,000	27,400,000
Number of Projects with Estimate Changes									3	5	1
Downward Estimate Change [Member] | Large Project Construction [Member] | Minimum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									(1,100,000)	(1,900,000)
Downward Estimate Change [Member] | Large Project Construction [Member] | Maximum [Member]
Change in Accounting Estimate [Line Items]
Range Of Effect On Gross Profit									$ (16,800,000)	$ (26,800,000)
Complete or Substantially Complete [Member] | Downward Estimate Change [Member] | Construction [Member]
Change in Accounting Estimate [Line Items]
Number of Projects with Estimate Changes									5