Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income after-tax	$ 5,596,000	$ 11,379,000	$ 7,762,000	$ 2,532,000	$ 4,351,000	$ 5,673,000	$ 4,468,000	$ (1,029,000)	$ 27,269,000	$ 13,463,000	$ (36,830,000)
Revenue	330,340,000	349,989,000	351,053,000	325,890,000	315,870,000	335,241,000	353,172,000	326,902,000	1,357,272,000	1,331,185,000	1,216,654,000
Cost of sales									1,117,389,000	1,123,564,000	1,035,124,000
Selling, general, and administrative expenses									194,214,000	185,809,000	167,053,000
Cash paid for:
Interest									799,000	1,326,000	1,720,000
Income taxes for continuing operations									15,821,000	13,948,000	1,613,000
Income taxes for discontinued operations										5,000	8,000
Total									16,620,000	15,279,000	3,341,000
Revenue Recognition
Percentage of revenue earned on a project basis									83.00%
Contracts in progress
Costs incurred on contracts in progress	989,072,000				1,182,085,000				989,072,000	1,182,085,000
Estimated earnings, net of losses	126,431,000				134,534,000				126,431,000	134,534,000
Less-Billings to date	(1,151,969,000)				(1,364,229,000)				(1,151,969,000)	(1,364,229,000)
Contracts in progress	(36,466,000)				(47,610,000)				(36,466,000)	(47,610,000)
Costs and estimated earnings in excess of billings	28,122,000				26,204,000				28,122,000	26,204,000
Billings in excess of costs and estimated earnings	(64,588,000)				(73,814,000)				(64,588,000)	(73,814,000)
Period during which progress billings or contract price can be withheld until completion of work									6 months
Retention receivable	51,400,000				48,000,000				51,400,000	48,000,000
Retention payable	10,300,000				11,300,000				10,300,000	11,300,000
Warranty Costs
Labor warranty period after servicing of existing HVAC system									30 days
Adjustments
Net income after-tax									1,300,000
Revenue									3,300,000
Cost of sales									800,000
Selling, general, and administrative expenses									$ 300,000