Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Assets and Liabilities, Lessee [Table Text Block]

Operating lease ROU assets:

(Millions of Dollars)	Dec. 31, 2019
PPAs	$	500.3
Other	48.0
Gross operating lease ROU assets	548.3
Accumulated amortization	(25.9		)
Net operating lease ROU assets	$	522.4

Lease, Cost [Table Text Block]

Components of lease expense:

(Millions of Dollars)	2019		2018		2017
Operating leases
PPA capacity payments	$	48.1	$	51.1	$	51.4
Other operating leases (a)	4.9		7.9		6.4
Total operating lease expense (b)	$	53.0	$	59.0	$	57.8

^(a)  Includes short-term lease expense of $1.5 million, $1.1 million and $1.2 million for 2019, 2018 and 2017, respectively.

^(b) 

PPA capacity payments are included in electric fuel and purchased power on the statements of income. Expense for other operating leases is included in O&M expense.

Lessee, Operating Lease, Liability, Maturity [Table Text Block]

Commitments under operating leases as of Dec. 31, 2019:

(Millions of Dollars)	PPA (a) (b) Operating Leases			Other Operating Leases			Total Operating Leases
2020	$	46.2		$	3.4		$	49.6
2021	46.2			3.3			49.5
2022	46.2			3.4			49.6
2023	46.2			3.4			49.6
2024	46.2			3.5			49.7
Thereafter	404.5			51.3			455.8
Total minimum obligation	635.5			68.3			703.8
Interest component of obligation	(160.0		)	(21.6		)	(181.6		)
Present value of minimum obligation	475.5			46.7			522.2
Less current portion							(26.9		)
Noncurrent operating lease liabilities							$	495.3
Weighted-average remaining lease term in years							14.1

^(a)  Amounts do not include PPAs accounted for as executory contracts and/or contingent payments, such as energy payments on renewable PPAs.

^(b) 

PPA operating leases contractually expire at various dates through 2033.

Estimated Minimum Purchases Under Fuel Contracts

Estimated minimum purchases under these contracts as of Dec. 31, 2019:

(Millions of Dollars)	Coal		Natural gas supply		Natural gas storage and transportation
2020	$	96.7	$	12.3	$	28.9
2021	67.7		—		23.3
2022	38.8		—		17.4
2023	—		—		12.7
2024	—		—		6.7
Thereafter	—		—		26.3
Total	$	203.2	$	12.3	$	115.3

Estimated Future Payments for Capacity and Energy Pursuant to Purchased Power Agreements

At Dec. 31, 2019, the estimated future payments for capacity that SPS is obligated to purchase pursuant to these executory contracts, subject to availability, were as follows:

(Millions of Dollars)	Capacity
2020	$	12.3
2021	12.5
2022	12.7
2023	13.0
2024	5.9
Thereafter	—
Total	$	56.4

Future Commitments Under Operating Leases

Commitments under operating leases as of Dec. 31, 2018:

(Millions of Dollars)	PPA (a) (b) Operating Leases		Other Operating Leases		Total Operating Leases
2019	$	46.7	$	5.2	$	51.9
2020	46.2		5.2		51.4
2021	46.2		5.1		51.3
2022	46.2		5.1		51.3
2023	46.2		5.1		51.3
Thereafter	450.8		56.3		507.1

^(a)  Amounts do not include PPAs accounted for as executory contracts and/or contingent payments, such as energy payments on renewable PPAs.

^(b) 

PPA operating leases contractually expire at various dates through 2033.

Asset Retirement Obligations

SPS’ AROs were as follows:

	2019
(Millions  of Dollars)	Jan. 1, 2019		Amounts Incurred (a)		Amounts Settled (b)			Accretion		Cash Flow Revisions (c)			Dec. 31, 2019
Electric
Steam and other production	$	22.0	$	—	$	(1.6	)	$	1.4	$	29.5		$	51.3
Wind	—		16.0		—			0.4		—			16.4
Distribution	9.1		—		—			0.4		—			9.5
Miscellaneous	1.3		—		—			—		(1.2		)	0.1
Total liability	$	32.4	$	16.0	$	(1.6	)	$	2.2	$	28.3		$	77.3

^(a)  Amounts incurred related to the Hale wind farm placed in service in 2019.

^(b)  Amounts settled related to asbestos abatement projects.

^(c)  In 2019, AROs were revised for changes in timing and estimates of cash flows. Changes in steam production AROs primarily related to the cost estimates to remediate ponds at production facilities.

	2018
(Millions  of Dollars)	Jan. 1, 2018		Accretion		Cash Flow Revisions (a)		Dec. 31, 2018 (b)
Electric
Steam and other production	$	20.3	$	1.2	$	0.5	$	22.0
Distribution	7.0		0.3		1.8		9.1
Miscellaneous	1.2		0.1		—		1.3
Total liability	$	28.5	$	1.6	$	2.3	$	32.4

^(a)  In 2018, AROs were revised for changes in timing and estimates of cash flows. Changes in electric distribution AROs were primarily related to increased labor costs.

^(b) 

There were no ARO amounts incurred or settled in 2018.