Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions | Mar. 02, 2016 | Mar. 06, 2015 | Jan. 13, 2015 | Dec. 18, 2014 | Mar. 31, 2016 | Mar. 31, 2015 |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared per share to shareholders | | | | | $ 0.25 | $ 0.40 |
Cash Distribution Approved on March 2, 2016 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distribution declaration date | | | | | Mar. 2, 2016 | |
Cash distributions to unit holders, date of record | | | | | Mar. 31, 2016 | |
Dividends Payable, date declared | | | | | Mar. 2, 2016 | |
Dividends payable date of record | | | | | Mar. 31, 2016 | |
Cash dividends declared per share to shareholders | $ 0.25 | | | | | |
Cash distribution and dividend paid date | | | | | Apr. 21, 2016 | |
Cash Distribution Approved on March 6, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distribution declaration date | | | | | Mar. 6, 2015 | |
Cash distributions to unit holders, date of record | | | | | Mar. 31, 2015 | |
Dividends Payable, date declared | | | | | Mar. 6, 2015 | |
Dividends payable date of record | | | | | Mar. 31, 2015 | |
Cash dividends declared per share to shareholders | | $ 0.14 | | | | |
Cash distribution and dividend paid date | | | | | Apr. 23, 2015 | |
Cash Distribution Approved on January 13, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distribution declaration date | | | | | Jan. 13, 2015 | |
Cash distributions to unit holders, date of record | | | | | Jan. 20, 2015 | |
Dividends Payable, date declared | | | | | Jan. 13, 2015 | |
Dividends payable date of record | | | | | Jan. 20, 2015 | |
Cash dividends declared per share to shareholders | | | $ 0.26 | | | |
Cash distribution and dividend paid date | | | | | Jan. 29, 2015 | |
Cash Distribution Approved on December 18, 2014 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distribution declaration date | | | | | Dec. 18, 2014 | |
Cash distributions to unit holders, date of record | | | | | Dec. 18, 2014 | |
Dividends Payable, date declared | | | | | Dec. 18, 2014 | |
Dividends payable date of record | | | | | Dec. 18, 2014 | |
Cash dividends declared per share to shareholders | | | | $ 0.31 | | |
Cash distribution and dividend paid date | | | | | Jan. 16, 2015 | |
Accumulated Deficit | Cash Distribution Approved on March 2, 2016 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | $ 10.9 | | | | | |
Accumulated Deficit | Cash Distribution Approved on March 6, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | $ 6.1 | | | | |
Accumulated Deficit | Cash Distribution Approved on January 13, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | | $ 9 | | | |
Accumulated Deficit | Cash Distribution Approved on December 18, 2014 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | | | $ 10.8 | | |
InfraREIT, L.L.C. | Cash Distribution Approved on March 2, 2016 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distributions declared to unit holders, per unit | $ 0.25 | | | | | |
Cash distribution to unit holders | $ 15.2 | | | | | |
InfraREIT, L.L.C. | Cash Distribution Approved on March 6, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distributions declared to unit holders, per unit | | $ 0.14 | | | | |
Cash distribution to unit holders | | $ 8.5 | | | | |
InfraREIT, L.L.C. | Cash Distribution Approved on January 13, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distributions declared to unit holders, per unit | | | $ 0.26 | | | |
Cash distribution to unit holders | | | $ 11.7 | | | |
InfraREIT, L.L.C. | Cash Distribution Approved on December 18, 2014 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash distributions declared to unit holders, per unit | | | | $ 0.31 | | |
Cash distribution to unit holders | | | | $ 14.1 | | |
InfraREIT, L.L.C. | Accumulated Deficit | Cash Distribution Approved on March 2, 2016 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | $ 10.9 | | | | | |
InfraREIT, L.L.C. | Accumulated Deficit | Cash Distribution Approved on March 6, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | $ 6.1 | | | | |
InfraREIT, L.L.C. | Accumulated Deficit | Cash Distribution Approved on January 13, 2015 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | | $ 9 | | | |
InfraREIT, L.L.C. | Accumulated Deficit | Cash Distribution Approved on December 18, 2014 | | | | | | |
Class Of Stock [Line Items] | | | | | | |
Cash dividends declared to shareholders | | | | $ 10.8 | | |