Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Use of Estimates
Project gain (loss)	$ 3,400	$ 3,400	$ (4,400)
Cash paid for:
Interest		1,408	1,764	$ 799
Income taxes		35,538	15,366	15,821
Total		$ 36,946	17,130	$ 16,620
Revenue Recognition
Percentage of revenue earned on a project basis		82.00%
Contracts in progress
Costs incurred on contracts in progress	1,135,279	$ 1,135,279	1,193,857
Estimated earnings, net of losses	188,243	188,243	151,950
Less-Billings to date	(1,377,581)	(1,377,581)	(1,395,633)
Contracts in progress	(54,059)	(54,059)	(49,826)
Costs and estimated earnings in excess of billings	31,338	31,338	27,620
Billings in excess of costs and estimated earnings	85,397	$ 85,397	77,446
Period during which progress billings or contract price can be withheld until completion of work		6 months
Retention receivable	51,600	$ 51,600	50,500
Retention payable	$ 7,800	$ 7,800	8,900
Warranty Costs
Labor warranty period after servicing of existing HVAC system		30 days
Income Taxes
Federal statutory income taxes rate (as a percent)		35.00%
Accounting Standards Update 201517 | Adjustments for New Accounting Principle, Early Adoption
New Accounting Pronouncements or Change in Accounting Principle
Deferred tax assets, noncurrent			19,400
Deferred tax liabilities, noncurrent			$ 300