Basis of Presentation - Reclassifications (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 segment	Mar. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of reportable segments	4
Cost of purchased water	$ 5,237	$ 4,388
Water assets sales price	8,993	7,390
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior year amortization reclassification adjustment		(1,085)
Mineral resources expenses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior year amortization reclassification adjustment		(338)
Corporate expenses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior year amortization reclassification adjustment		338,000
Hay Sales, Centennial Operations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior year amortization reclassification adjustment		(265)
Hay Sales, Centennial Operations | Cost of Sales
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior year amortization reclassification adjustment		$ (191)