Investments in Water Assets Investments in Water Assets - Tangible Water Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Long Lived Assets Held-for-sale [Line Items]
Total tangible water	$ 18,421	$ 13,854
Banked water and water for future delivery
Long Lived Assets Held-for-sale [Line Items]
Total tangible water	5,070	4,779
Transferable water
Long Lived Assets Held-for-sale [Line Items]
Total tangible water	$ 13,351	$ 9,075