Construction Joint Ventures (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Construction Joint Venture
Line Item Revenue	$ 464,624	$ 427,018	$ 1,005,457	$ 921,143
Net cash provided (used in) operating activities			(20,300)	(8,129)
Unconsolidated Construction Joint Venture
Construction Joint Venture
Performance Guarantees	83,100	65,100	83,100	65,100	$ 65,500
Partnership Interest [Member] | Unconsolidated Construction Joint Venture
Construction Joint Venture
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures	$ 5,400,000		$ 5,400,000
Joint Venture Consolidated | Consolidated Construction Joint Venture
Construction Joint Venture
Number of Active Joint Venture Projects	5		5
Line Item Revenue	$ 24,800	14,000	$ 79,900	39,000
Joint Venture Unconsolidated | Unconsolidated Construction Joint Venture
Construction Joint Venture
Number of Active Joint Venture Projects	12		12
Joint Venture Unconsolidated | Line Item Joint Venture
Construction Joint Venture
Number of Active Joint Venture Projects	4		4
Line Item Revenue	$ 9,500	$ 2,200	$ 23,500	18,000
Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture
Construction Joint Venture
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures	1,700,000		1,700,000
Other Partners Interest in Partnerships [Member] | Unconsolidated Construction Joint Venture
Construction Joint Venture
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures	3,700,000		3,700,000
Minimum | Joint Venture Consolidated | Consolidated Construction Joint Venture
Construction Joint Venture
Construction Contract Value	46,500		46,500
Revenue Remaining to be Recognized on Consolidated Construction Joint Ventures	$ 7,700		$ 7,700
Proportionate Share of the Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly	50.00%		50.00%
Net cash provided (used in) operating activities			$ 7,800	$ (16,800)
Minimum | Joint Venture Unconsolidated | Unconsolidated Construction Joint Venture
Construction Joint Venture
Construction Contract Value	$ 78,500		$ 78,500
Proportionate Share of the Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly	20.00%		20.00%
Minimum | Joint Venture Unconsolidated | Line Item Joint Venture
Construction Joint Venture
Construction Contract Value	$ 42,200		$ 42,200
Revenue Per Project Remaining to be Recognized on Line Item Construction Joint Ventures	200		200
Minimum | Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture
Construction Joint Venture
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures	900		900
Minimum | Reporting Entitys Interest in Joint Venture [Member] | Line Item Joint Venture
Construction Joint Venture
Construction Contract Value	28,300		28,300
Maximum | Joint Venture Consolidated | Consolidated Construction Joint Venture
Construction Joint Venture
Construction Contract Value	291,200		291,200
Revenue Remaining to be Recognized on Consolidated Construction Joint Ventures	$ 181,100		$ 181,100
Proportionate Share of the Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly	65.00%		65.00%
Maximum | Joint Venture Unconsolidated | Unconsolidated Construction Joint Venture
Construction Joint Venture
Construction Contract Value	$ 3,600,000		$ 3,600,000
Proportionate Share of the Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly	50.00%		50.00%
Maximum | Joint Venture Unconsolidated | Line Item Joint Venture
Construction Joint Venture
Construction Contract Value	$ 87,800		$ 87,800
Revenue Per Project Remaining to be Recognized on Line Item Construction Joint Ventures	23,600		23,600
Maximum | Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture
Construction Joint Venture
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures	527,600		527,600
Maximum | Reporting Entitys Interest in Joint Venture [Member] | Line Item Joint Venture
Construction Joint Venture
Construction Contract Value	$ 64,900		$ 64,900