Income Taxes - Interest Income (Expense) Related to Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Interest income related to income taxes	$ 4,398	$ 0	$ 146
Public Service Company of New Mexico [Member]
Income Taxes [Line Items]
Interest income related to income taxes	3,625	0	148
Texas-New Mexico Power Company [Member]
Income Taxes [Line Items]
Interest income related to income taxes	345	$ 0	$ (2)
Interest Income and Interest Expense applicable to federal income tax matters [Member]
Income Taxes [Line Items]
Net refunds received	6,500
Increase (decrease) of net interest receivable	(2,100)
Interest income	5,100
Interest expense	700
Professional fees	900
Net pre-tax impacts	3,500
Interest Income and Interest Expense applicable to federal income tax matters [Member] | Public Service Company of New Mexico [Member]
Income Taxes [Line Items]
Net pre-tax impacts	2,600
Interest Income and Interest Expense applicable to federal income tax matters [Member] | Texas-New Mexico Power Company [Member]
Income Taxes [Line Items]
Net pre-tax impacts	300
Interest Income and Interest Expense applicable to federal income tax matters [Member] | Corporate and Other [Member]
Income Taxes [Line Items]
Net pre-tax impacts	$ 600