Long-Term Water Assets - Volume of Water Assets (Details) - acre ft	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2009	Dec. 31, 2008
Banked water and water for future delivery
Water contracts and purchased water	10,137,000	10,137,000
Total purchased water contracts	85,784,000	83,980,000
Total purchased and contracted water sources in acre feet	142,132,000	133,306,000
AVEK water bank
Banked water and water for future delivery
AVEK water bank	13,033,000	13,033,000	6,393	8,393
Company water bank	37,316,000	35,793,000
Transferable water	5,999,000	500,000
Banked water and water for future delivery	56,348,000	49,326,000
WRMWSD - Contracts with Company
Banked water and water for future delivery
Water contracts and purchased water	15,547,000	15,547,000
Tejon-Castac Water District
Banked water and water for future delivery
Banked water and water for future delivery	54,351,000	52,547,000
Water contracts and purchased water	5,749,000	5,749,000