Earnings Per Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic net income per share:
Net income attributable to InfraREIT, Inc.	$ 19,806	$ 13,972	$ 6,362	$ (26,873)	$ 2,924	$ 11,894	$ 4,235	$ 3,845	$ 13,267	$ 22,898	$ 32,122
Weighted average common shares outstanding									42,983	35,053	29,883
Basic net income per share	$ 0.45	$ 0.32	$ 0.15	$ (0.65)	$ 0.08	$ 0.34	$ 0.12	$ 0.11	$ 0.31	$ 0.65	$ 1.07
Diluted net income per share:
Net income attributable to InfraREIT, Inc.	$ 19,806	$ 13,972	$ 6,362	$ (26,873)	$ 2,924	$ 11,894	$ 4,235	$ 3,845	$ 13,267	$ 22,898	$ 32,122
Weighted average common shares outstanding									42,983	35,053	29,883
Weighted average dilutive shares outstanding									42,983	35,053	29,883
Diluted net income per share	$ 0.45	$ 0.32	$ 0.15	$ (0.65)	$ 0.08	$ 0.34	$ 0.12	$ 0.11	$ 0.31	$ 0.65	$ 1.07
Due to the anti-dilutive effect, the computation of diluted earnings per share does not reflect the following adjustments:
Net income attributable to noncontrolling interest	$ 7,725	$ 5,458	$ 2,481	$ (9,000)	$ 836	$ 3,621	$ 1,278	$ 1,147	$ 6,664	$ 6,882	$ 10,288
Redemption of operating partnership units									16,232	10,578	9,181