Financing - PNMR and Its Subsidiaries and Short-term Debt (Details) - USD ($)	Feb. 19, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 08, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Weighted average borrowing rate		6.60%	6.60%		6.90%
Short-term debt		$ 250,600,000	$ 105,600,000
Letters of credit outstanding		$ 6,200,000
PNMR Term Loan Agreement [Member]
Short-term Debt [Line Items]
Weighted average borrowing rate		1.26%
Short-term debt		$ 150,000,000	100,000,000
PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		$ 300,000,000
Weighted average borrowing rate		1.67%
Short-term debt		$ 41,600,000	600,000
TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Weighted average borrowing rate		1.29%
Subsequent Event [Member]
Short-term Debt [Line Items]
Invested cash	$ 1,900,000
Subsequent Event [Member] | PNMR Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity	187,700,000
Subsequent Event [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity	598,200,000
Texas-New Mexico Power Company [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate		$ 11,800,000	22,700,000
Short-term debt		59,000,000	5,000,000
Letters of credit outstanding		100,000
Texas-New Mexico Power Company [Member] | TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		75,000,000
Short-term debt		59,000,000	5,000,000
Texas-New Mexico Power Company [Member] | TNMP Revolving Credit Facility [Member] | First Mortgage Bonds Due 2014, Series 2009A, at 9.50% [Member]
Short-term Debt [Line Items]
Securities received as collateral		75,000,000
Texas-New Mexico Power Company [Member] | Subsequent Event [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate	15,100,000
Invested cash	0
Texas-New Mexico Power Company [Member] | Subsequent Event [Member] | TNMP Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity	59,900,000
Public Service Company of New Mexico [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate		0	0
Letters of credit outstanding		3,200,000
Public Service Company of New Mexico [Member] | New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity				$ 50,000,000.0
Public Service Company of New Mexico [Member] | PNM Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		400,000,000
Short-term debt		0	0
Public Service Company of New Mexico [Member] | New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Short-term debt		0	$ 0
Public Service Company of New Mexico [Member] | Subsequent Event [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate	0
Invested cash	0
Public Service Company of New Mexico [Member] | Subsequent Event [Member] | PNM Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity	350,600,000
Public Service Company of New Mexico [Member] | Subsequent Event [Member] | New Mexico Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Available borrowing capacity	$ 0
Maximum [Member]
Short-term Debt [Line Items]
Short-term debt - affiliate		$ 100,000,000