Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)				0 Months Ended	1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Sep. 28, 2012	Sep. 28, 2012 Credo [Member]	Sep. 28, 2012 Credo [Member]	Dec. 31, 2013 Credo [Member]	Dec. 31, 2013 Water Resources Company [Member]	Dec. 31, 2010 Water Resources Company [Member] Groundwater Leases [Member]	Dec. 31, 2013 Patents [Member] Credo [Member]	Sep. 28, 2012 Patents [Member] Credo [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired on acquisition	$ 64,493,000	$ 61,680,000				$ 60,619,000	$ 3,874,000
Acquisition of outstanding stock of Credo			100.00%	100.00%	100.00%
Purchase price of acquisitions, per share amount				$ 14.50	$ 14.50
Equity purchase price of transaction				146,445,000
Payment of Credo's outstanding debt				8,770,000	8,770,000
Identified intangible assets								1,681,000
Identified intangibles , related to patents										590,000
Identified intangibles , net									$ 472,000