Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2015

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

The components of regulatory assets shown on the balance sheets of SPS at Dec. 31, 2015 and 2014 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2015				Dec. 31, 2014
Regulatory Assets			Current		Noncurrent		Current		Noncurrent
Pension and retiree medical obligations (a)	7	Various	$	15,632	$	223,122	$	17,256	$	240,980
Recoverable deferred taxes on AFUDC recorded in plant	1	Plant lives	—		39,368		—		36,878
Net AROs (b)	11	Plant lives	—		23,014		—		21,689
Conservation programs (c)	1	One to three years	5,137		3,859		3,451		5,020
Renewable resources and environmental initiatives	11	One to two years	3,740		2,019		6,726		5,124
Losses on reacquired debt	4	Term of related debt	850		1,743		1,104		2,594
Deferred income tax adjustment	1, 6	Typically plant lives	—		170		—		302
Recoverable electric energy costs	1	Less than one year	12		—		513		—
Texas Surcharge	10	Less than one year	—		—		15,388		—
Other		Various	6,170		8,519		7,568		10,718
Total regulatory assets			$	31,541	$	301,814	$	52,006	$	323,305

^(a)  Includes the non-qualified pension plan.

^(b)  Includes amounts recorded for future recovery of AROs.

^(c)  Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.

Regulatory Liabilities

The components of regulatory liabilities shown on the balance sheets of SPS at Dec. 31, 2015 and 2014 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2015				Dec. 31, 2014
Regulatory Liabilities			Current		Noncurrent		Current		Noncurrent
Plant removal costs	11	Plant lives	$	—	$	203,954	$	—	$	68,106
Revenue subject to refund	10	One to two years	20,647		1,080		7,527		19,518
Renewable resources and environmental    initiatives	11	One to two years	2,960		880		1,120		765
Gain from asset sales	10	Various	2,640		2,584		2,577		4,468
Deferred electric energy costs	1	Less than one year	61,041		—		53,971		—
Contract valuation adjustments (a)	1, 9	Term of related contract	9,387		—		20,211		2,521
Conservation programs (b)	1	Less than one year	645		—		1,425		—
Other		Various	985		21,086		892		19,810
Total regulatory liabilities (c)			$	98,305	$	229,584	$	87,723	$	115,188

^(a)  Includes the fair value of certain long-term PPAs used to meet energy capacity requirements.

^(b)  Includes costs for conservation programs as well as incentives allowed in certain jurisdictions.

^(c)  Revenue subject to refund of $3.9 million and $51.2 million for 2015 and 2014, respectively, is included in other current liabilities.