Pension and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures

A reconciliation of the changes in Level 3 fair value measurements is as follows:

	Fixed Income - Corporate
PNMR Master Trust	PNM Pension			TNMP Pension			Total Master Trust
	(In thousands)
Balance at December 31, 2015	$	719		$	78		$	797
Actual return on assets sold during the period	1			—			1
Actual return on assets still held at period end	19			2			21
Purchases	—			—			—
Sales	(387		)	(42		)	(429		)
Balance at December 31, 2016	352			38			390
Actual return on assets sold during the period	1			—			1
Actual return on assets still held at period end	(7		)	(1		)	(8		)
Purchases	92			10			102
Sales	(247		)	(26		)	(273		)
Balance at December 31, 2017	$	191		$	21		$	212

The following table presents information about the PBO, fair value of plan assets, and funded status of the plans:

	PNM Plan						TNMP Plan
	Year Ended December 31,						Year Ended December 31,
	2017			2016			2017			2016
	(In thousands)
PBO at beginning of year	$	621,751		$	597,900		$	67,061		$	64,198
Service cost	—			—			—			—
Interest cost	26,908			30,307			2,887			3,304
Actuarial (gain) loss	26,298			39,463			3,050			4,318
Benefits paid	(50,974		)	(45,919		)	(4,575		)	(4,759		)
PBO at end of year	623,983			621,751			68,423			67,061
Fair value of plan assets at beginning of year	543,601			557,923			60,624			62,082
Actual return on plan assets	69,389			31,597			7,450			3,301
Employer contributions	—			—			—			—
Benefits paid	(50,974		)	(45,919		)	(4,575		)	(4,759		)
Fair value of plan assets at end of year	562,016			543,601			63,499			60,624
Funded status – asset (liability) for pension benefits	$	(61,967	)	$	(78,150	)	$	(4,924	)	$	(6,437	)

The following table presents information about the APBO, the fair value of plan assets, and the funded status of the plans:

	PNM Plan						TNMP Plan
	Year Ended December 31,						Year Ended December 31,
	2017			2016			2017			2016
	(In thousands)
APBO at beginning of year	$	94,269		$	84,674		$	12,830		$	13,106
Service cost	96			140			143			186
Interest cost	4,025			4,346			556			677
Participant contributions	3,069			2,690			379			520
Actuarial (gain) loss	(1,601		)	17,877			(381		)	(96		)
Benefits paid	(9,961		)	(11,734		)	(1,248		)	(1,563		)
Plan design changes	—			(3,724		)	—			—
APBO at end of year	89,897			94,269			12,279			12,830
Fair value of plan assets at beginning of year	72,694			72,952			8,544			9,111
Actual return on plan assets	14,222			5,923			1,642			476
Employer contributions	332			2,863			685			—
Participant contributions	3,069			2,690			379			520
Benefits paid	(9,961		)	(11,734		)	(1,248		)	(1,563		)
Fair value of plan assets at end of year	80,356			72,694			10,002			8,544
Funded status – asset (liability)	$	(9,541	)	$	(21,575	)	$	(2,277	)	$	(4,286	)

Schedule of Assumptions Used

The following significant weighted-average assumptions were used to determine the PBO and net periodic benefit cost (income). Should actual experience differ from actuarial assumptions, the PBO and net periodic benefit cost (income) would be affected.

	Year Ended December 31,
PNM Plan	2017		2016		2015
Discount rate for determining December 31 PBO	4.05	%	4.51	%	5.29	%
Discount rate for determining net periodic benefit cost (income)	4.51	%	5.29	%	4.48	%
Expected return on plan assets	6.40	%	6.50	%	6.80	%
Rate of compensation increase	N/A		N/A		N/A
TNMP Plan
Discount rate for determining December 31 PBO	4.01	%	4.49	%	5.39	%
Discount rate for determining net periodic benefit cost (income)	4.49	%	5.39	%	4.39	%
Expected return on plan assets	6.40	%	6.50	%	6.80	%
Rate of compensation increase	N/A		N/A		N/A

Actuarial (gain) loss results from changes in:

	PNM Plan						TNMP Plan
	Year Ended December 31,						Year Ended December 31,
	2017			2016			2017			2016
	(in thousands)
Discount rates	$	27,547		$	41,849		$	3,528		$	5,055
Demographic experience	(1,249		)	(334		)	(517		)	(556		)
Other assumption and experience	—			(2,052		)	39			(181		)
	$	26,298		$	39,463		$	3,050		$	4,318

Actuarial (gain) loss results from changes in:

	PNM Plan						TNMP Plan
	Year Ended December 31,						Year Ended December 31,
	2017			2016			2017			2016
	(in thousands)
Discount rates	$	3,536		$	6,569		$	613		$	1,112
Claims, contributions, and demographic experience	(5,845		)	19,562			(994		)	(102		)
Assumed participation rate	—			(6,335		)	—			(1,013		)
Mortality rate	—			(691		)	—			(93		)
Medical benefits	1,425			(1,228		)	—			—
Dental trend assumption	(717		)	—			—			—
	$	(1,601	)	$	17,877		$	(381	)	$	(96	)

The following significant weighted-average assumptions were used to determine the APBO and net periodic benefit cost. Should actual experience differ from actuarial assumptions, the APBO and net periodic benefit cost would be affected.

	Year Ended December 31,
PNM Plan	2017		2016		2015
Discount rate for determining December 31 APBO	4.00	%	4.47	%	5.34	%
Discount rate for determining net periodic benefit cost	4.47	%	5.34	%	4.45	%
Expected return on plan assets	7.50	%	7.70	%	7.70	%
Rate of compensation increase	N/A		N/A		N/A
TNMP Plan
Discount rate for determining December 31 APBO	4.00	%	4.47	%	5.34	%
Discount rate for determining net periodic benefit cost	4.47	%	5.34	%	4.45	%
Expected return on plan assets	5.40	%	5.70	%	5.70	%
Rate of compensation increase	N/A		N/A		N/A

The following significant weighted-average assumptions were used to determine the PBO and net periodic benefit cost. Should actual experience differ from actuarial assumptions, the PBO and net periodic benefit cost would be affected.

	Year Ended December 31,
PNM Plan	2017		2016		2015
Discount rate for determining December 31 PBO	4.05	%	4.51	%	5.29	%
Discount rate for determining net periodic benefit cost	4.51	%	5.29	%	4.48	%
Long-term rate of return on plan assets	N/A		N/A		N/A
Rate of compensation increase	N/A		N/A		N/A
TNMP Plan
Discount rate for determining December 31 PBO	4.01	%	4.49	%	5.39	%
Discount rate for determining net periodic benefit cost	4.49	%	5.39	%	4.39	%
Long-term rate of return on plan assets	N/A		N/A		N/A
Rate of compensation increase	N/A		N/A		N/A

Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year

The following table presents pre-tax information about net actuarial loss in AOCI as of December 31, 2017.

	December 31, 2017
	PNM Plan			TNMP Plan
	(In thousands)
Amount in AOCI not yet recognized in net periodic benefit cost at beginning of year	$	2,299		$	—
Experience (gain) loss	674			44
Regulatory asset (liability) adjustment	(391		)	(44		)
Amortization recognized in net periodic benefit cost (income)	(132		)	—
Amount in AOCI not yet recognized in net periodic benefit cost at end of year	$	2,450		$	—
Amortization expected to be recognized in 2018	$	151		$	—

The following table presents pre-tax information about prior service cost and net actuarial (gain) loss in AOCI as of December 31, 2017.

	PNM Plan						TNMP Plan
	December 31, 2017						December 31, 2017
	Prior service cost			Net actuarial (gain) loss			Net actuarial (gain) loss
	(In thousands)
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at beginning of year	$	(1,450	)	$	159,149		$	—
Experience (gain) loss	—			(9,288		)	(621		)
Regulatory asset (liability) adjustment	—			5,387			621
Amortization recognized in net periodic benefit cost (income)	405			(6,722		)	—
Amounts in AOCI not yet recognized in net periodic benefit cost (income) at end of year	$	(1,045	)	$	148,526		$	—
Amortization expected to be recognized in 2018	$	(405	)	$	6,653		$	—

Schedule of Net Benefit Costs

The following table presents the components of net periodic benefit cost:

	Year Ended December 31,
	2017		2016		2015
	(In thousands)
PNM Plan
Service cost	$	—	$	—	$	—
Interest cost	697		812		760
Amortization of net (gain) loss	313		256		325
Amortization of prior service cost	—		—		—
Net periodic benefit cost	$	1,010	$	1,068	$	1,085
TNMP Plan
Service cost	$	—	$	—	$	—
Interest cost	33		40		36
Amortization of net (gain) loss	9		2		5
Amortization of prior service cost	—		—		—
Net periodic benefit cost	$	42	$	42	$	41

The following table presents the components of net periodic benefit cost (income):

	Year Ended December 31,
	2017			2016			2015
	(In thousands)
PNM Plan
Service cost	$	—		$	—		$	—
Interest cost	26,908			30,307			28,255
Expected return on plan assets	(33,803		)	(35,416		)	(39,323		)
Amortization of net (gain) loss	16,006			13,820			14,820
Amortization of prior service cost	(965		)	(965		)	(965		)
Net periodic benefit cost	$	8,146		$	7,746		$	2,787
TNMP Plan
Service cost	$	—		$	—		$	—
Interest cost	2,887			3,304			3,043
Expected return on plan assets	(3,779		)	(3,943		)	(4,420		)
Amortization of net (gain) loss	923			700			782
Amortization of prior service cost	—			—			—
Net periodic benefit cost (income)	$	31		$	61		$	(595	)

The following table presents the components of net periodic benefit cost:

	Year Ended December 31,
	2017			2016			2015
	(In thousands)
PNM Plan
Service cost	$	96		$	140		$	204
Interest cost	4,025			4,346			4,089
Expected return on plan assets	(5,230		)	(5,483		)	(5,610		)
Amortization of net (gain) loss	3,682			1,145			1,966
Amortization of prior service credit	(1,663		)	(30		)	(642		)
Net periodic benefit cost	$	910		$	118		$	7
TNMP Plan
Service cost	$	143		$	186		$	247
Interest cost	556			677			608
Expected return on plan assets	(456		)	(490		)	(520		)
Amortization of net (gain) loss	(79		)	(40		)	—
Amortization of prior service cost	—			—			—
Net periodic benefit cost	$	164		$	333		$	335

Schedule of Expected Benefit Payments

The following pension benefit payments are expected to be paid:

	PNM Plan		TNMP Plan
	(In thousands)
2018	$	49,221	$	5,929
2019	48,639		5,215
2020	47,069		5,108
2021	45,246		5,373
2022	44,232		4,856
2023 - 2027	201,389		22,085

The following other postretirement benefit payments, which reflect expected future service and are net of participant contributions, are expected to be paid:

	PNM Plan		TNMP Plan
	(In thousands)
2018	$	7,829	$	708
2019	7,730		725
2020	7,605		748
2021	7,442		774
2022	7,132		795
2023 - 2027	31,250		4,126

The following executive retirement plan payments, which reflect expected future service, are expected:

	PNM Plan		TNMP Plan
	(In thousands)
2018	$	1,501	$	93
2019	1,473		91
2020	1,441		89
2021	1,405		85
2022	1,363		81
2023 - 2027	6,014		324

Schedule of Health Care Cost Trend Rates

The following table shows the assumed health care cost trend rates for the PNM postretirement benefit plan:

	PNM Plan
	December 31,
	2017		2016
Health care cost trend rate assumed for next year	6.5	%	6.8	%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate)	5.0	%	5.0	%
Year that the rate reaches the ultimate trend rate	2024		2024

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates

The following table shows the impact of a one-percentage-point change in assumed health care cost trend rates:

	PNM Plan
	1-Percentage- Point  Increase		1-Percentage- Point  Decrease
	(In thousands)
Effect on total of service and interest cost	$	72	$	(111	)
Effect on APBO	$	1,452	$	(2,235	)

Schedule of Net Funded Status

For the executive retirement programs, the following table presents information about the PBO and funded status of the plans:

	PNM Plan						TNMP Plan
	Year Ended December 31,						Year Ended December 31,
	2017			2016			2017			2016
	(In thousands)
PBO at beginning of year	$	16,212		$	16,105		$	787		$	794
Service cost	—			—			—			—
Interest cost	697			812			33			40
Actuarial (gain) loss	674			768			44			47
Benefits paid	(1,466		)	(1,473		)	(93		)	(94		)
PBO at end of year – funded status	16,117			16,212			771			787
Less current liability	1,501			1,510			93			93
Non-current liability	$	14,616		$	14,702		$	678		$	694

Summary of Expenses for Other Retirement Plans

A summary of expenses for these other retirement plans is as follows:

	Year Ended December 31,
	2017		2016		2015
	(In thousands)
PNMR
401(k) plan	$	16,452	$	17,762	$	16,725
Non-qualified plan	$	3,702	$	2,017	$	1,436
PNM
401(k) plan	$	12,120	$	13,397	$	12,679
Non-qualified plan	$	2,834	$	1,535	$	1,090
TNMP
401(k) plan	$	4,332	$	4,365	$	4,046
Non-qualified plan	$	868	$	482	$	346