Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Credo [Member]	Dec. 31, 2010 Water Resources Company [Member]	Dec. 31, 2012 Patents [Member] Credo [Member]	Dec. 31, 2010 Groundwater Leases [Member] Water Resources Company [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired on acquisition	$ 61,680,000	$ 3,874,000	$ 57,806,000	$ 3,874,000
Identified intangibles , related to patents					590,000
Identified intangibles , net	$ 2,188,000	$ 1,577,000			$ 566,400	$ 1,622,000