Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2010
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired on acquisition	$ 61,164,000	$ 63,423,000
Oil and Gas Properties [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired on acquisition	57,290,000	59,549,000
Water Resources Company [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Goodwill acquired on acquisition		3,874,000
Water Resources Company [Member] | Groundwater Leases [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Identified intangible assets			$ 1,681,000
Patents [Member] | Credo [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Identified intangibles, net	$ 283,000
Multi Family Property [Member] | Austin, Texas [Member]
Schedule Of Goodwill And Other Intangible Assets [Line Items]
Identified intangibles, net		$ 865,000