Quarterly Results (Unaudited) Quarterly Results Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								4 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Results [Line Items]
Revenues	$ 550,776	$ 486,747	$ 503,082	$ 477,592	$ 495,713	$ 506,859	$ 513,024	$ 497,590		$ 2,018,197	$ 2,013,186	$ 1,883,533
Gross Profit	174,751	165,318	177,860	157,225	156,663	170,749	169,705	163,203		675,154	660,320	556,685
Net Income (Loss) Attributable to Parent	$ 1,780	$ 25,576	$ 14,097	$ 15,845	$ 11,649	$ (9,885)	$ 19,917	$ 10,089		$ 57,298	$ 31,770	$ 12,678
Earnings per common share - Basic	$ 0.05	$ 0.66	$ 0.36	$ 0.41	$ 0.30	$ (0.26)	$ 0.52	$ 0.27		$ 1.48	$ 0.83	$ 0.33
Earnings per common share - Diluted	0.05	$ 0.65	$ 0.36	$ 0.40	$ 0.30	$ (0.26)	$ 0.52	$ 0.26		$ 1.45	$ 0.82	$ 0.33
Unusual or Infrequent Item, or Both, Insurance Proceeds			$ 8,000							$ 8,000
Restructuring Charges										6,418	$ 49,090	$ (7,263)
Warranty Expense										(2,054)	13,920	45,984
2016 Projects [Member]
Quarterly Results [Line Items]
Restructuring Charges					$ 7,800	$ 40,000			$ 47,794	6,418
Water Operating Segment [Member]
Quarterly Results [Line Items]
Revenues										461,634	505,336	519,422
Gross Profit										164,898	$ 172,580	$ 145,680
Water Operating Segment [Member] | 2016 Projects [Member]
Quarterly Results [Line Items]
Restructuring Charges									$ 13,061	700
Tax Cuts and Jobs Act [Domain]
Quarterly Results [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions										$ 30,400
Earnings per common share - Basic	0.79
Earnings per common share - Diluted	$ 0.77
Insurance Recovery, net of tax [Member] | Water Operating Segment [Member]
Quarterly Results [Line Items]
Earnings per common share - Basic			$ 0.13							$ 0.13
Earnings per common share - Diluted			$ 0.12							$ 0.12