Earnings Per Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic net income per share:
Net income attributable to InfraREIT, Inc.	$ 19,990	$ 17,041	$ 6,608	$ 6,315	$ 19,806	$ 13,972	$ 6,362	$ (26,873)	$ 49,954	$ 13,267	$ 22,898
Weighted average common shares outstanding									43,668,000	42,983,000	35,053,000
Basic net income per share	$ 0.46	$ 0.39	$ 0.15	$ 0.14	$ 0.45	$ 0.32	$ 0.15	$ (0.65)	$ 1.14	$ 0.31	$ 0.65
Diluted net income per share:
Net income attributable to InfraREIT, Inc.	$ 19,990	$ 17,041	$ 6,608	$ 6,315	$ 19,806	$ 13,972	$ 6,362	$ (26,873)	$ 49,954	$ 13,267	$ 22,898
Weighted average common shares outstanding									43,668,000	42,983,000	35,053,000
Redemption of Operating Partnership units									186,496
Weighted average dilutive shares outstanding									43,668,000	42,983,000	35,053,000
Diluted net income per share	$ 0.46	$ 0.39	$ 0.15	$ 0.14	$ 0.45	$ 0.32	$ 0.15	$ (0.65)	$ 1.14	$ 0.31	$ 0.65
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	$ 7,749	$ 6,560	$ 2,576	$ 2,462	$ 7,725	$ 5,458	$ 2,481	$ (9,000)	$ 19,347	$ 6,664	$ 6,882
Redemption of Operating Partnership units									16,968,000	16,232,000	10,578,000