Pension and Other Postretirement Benefits - Other Postretirement Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Retirement Plans, 401 (k) plan [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
401(k) plan	$ 17,762	$ 16,725	$ 16,703
Other Retirement Plans, 401 (k) plan [Member] | Public Service Company of New Mexico [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
401(k) plan	13,397	12,679	12,745
Other Retirement Plans, 401 (k) plan [Member] | Texas-New Mexico Power Company [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
401(k) plan	4,365	4,046	3,958
Other Retirement Plans, Key Employees, Non-qualified Plan [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Non-qualified plan	2,017	1,436	2,257
Other Retirement Plans, Key Employees, Non-qualified Plan [Member] | Public Service Company of New Mexico [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Non-qualified plan	1,535	1,090	1,722
Other Retirement Plans, Key Employees, Non-qualified Plan [Member] | Texas-New Mexico Power Company [Member]
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Non-qualified plan	$ 482	$ 346	$ 535