Military Privatization (Details) (USD $)	12 Months Ended				12 Months Ended		0 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Military Utility Privatization Subsidiaries	Dec. 31, 2011 Military Utility Privatization Subsidiaries	Apr. 30, 2012 Military Utility Privatization Subsidiaries Contract modification	Sep. 30, 2012 Military Utility Privatization Subsidiaries Contract modification	Mar. 31, 2012 Military Utility Privatization Subsidiaries Contract modification item	Dec. 31, 2011 Military Utility Privatization Subsidiaries Contract modification
Military Privatization
Percentage of recovery of investment in assets of water and/or wastewater systems at various military bases					100.00%
Period of fixed price contracts to operate and maintain the water and/or wastewater systems at various military bases (in years)					50 years
Period during which renewal and replacement costs are covered under the contracts (in years)					2 years
Initial contract period					2 years
Price redetermination interval					3 years
Revenues recognized net of billings to date
Revenues (costs and estimated earnings) recognized on uncompleted contracts					$ 62,902,000	$ 36,160,000
Less: Billings to date					(37,335,000)	(31,341,000)
Total					25,567,000	4,819,000
Amount included in accompanying balance sheets
Costs and estimated earnings in excess of billings on uncompleted contracts					38,139,000	35,064,000
Billings in excess of costs and estimated earnings on uncompleted contracts					(12,572,000)	(30,245,000)
Total					25,567,000	4,819,000
Receivables from the U.S. government:
Billed receivables from the U.S. government					12,913,000	7,456,000
Unbilled receivables from the U.S. government					4,535,000	6,788,000
Less: allowance for doubtful accounts	(1,228,000)	(1,048,000)	(1,051,000)	(1,158,000)	(8,000)
Total					17,440,000	14,244,000
Amount of contract modification received							58,000,000	17,600,000	11,000,000
Number of projects									2
Aggregate amount of contract modification received									23,000,000
Pretax income
Increase in pretax operating income	$ 111,094,000	$ 95,104,000	$ 73,819,000		$ 24,608,000	$ 11,855,000	$ 820,000			$ 2,900,000