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	$	556.3
Other	72.2
Gross operating lease ROU assets	628.5
Accumulated amortization	(64.7		)
Net operating lease ROU assets	$	563.8

Lease, Cost [Table Text Block]

Components of lease expense:

(Millions of Dollars)	2019		2018		2017
Operating leases
PPA capacity payments	$	75.9	$	62.5	$	62.7
Other operating leases (a)	9.1		13.7		14.2
Total operating lease expense (b)	$	85.0	$	76.2	$	76.9

^(a)  Includes short-term lease expense of $1.4 million, $2.0 million and $2.7 million for 2019, 2018 and 2017, respectively.

^(b) 

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

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	$	93.5		$	7.9		$	101.4
2021	94.9			8.0			102.9
2022	96.4			11.9			108.3
2023	97.9			7.0			104.9
2024	99.5			6.8			106.3
Thereafter	119.8			44.9			164.7
Total minimum obligation	602.0			86.5			688.5
Interest component of obligation	(66.2		)	(16.7		)	(82.9		)
Present value of minimum obligation	$	535.8		$	69.8		605.6
Less current portion							(79.9		)
Noncurrent operating lease liabilities							$	525.7
Weighted-average remaining lease term in years							6.7

^(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 2026.

Estimated Minimum Purchases Under Fuel Contracts

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

(Millions of Dollars)	Coal		Nuclear fuel		Natural gas supply		Natural gas storage and transportation
2020	$	171.3	$	53.8	$	36.8	$	133.0
2021	85.2		102.5		1.4		129.8
2022	51.9		85.3		0.8		124.3
2023	35.1		103.0		—		107.8
2024	0.9		74.5		—		101.1
Thereafter	2.6		275.1		—		273.6
Total (a)	$	347.0	$	694.2	$	39.0	$	869.6

^(a) 

Includes amounts allocated to NSP-Wisconsin through intercompany charges.

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

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

(Millions of Dollars)	Capacity		Energy (a)
2020	$	54.5	$	109.4
2021	62.2		157.3
2022	61.3		172.9
2023	62.8		176.9
2024	64.5		181.8
Thereafter	45.4		146.3
Total (b)	$	350.7	$	944.6

^(a)  Excludes contingent energy payments for renewable energy PPAs.

^(b) 

Includes amounts allocated to NSP-Wisconsin through intercompany charges.

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	$	65.0	$	13.5	$	78.5
2020	66.1		8.4		74.5
2021	67.1		8.4		75.5
2022	68.2		8.1		76.3
2023	69.3		7.3		76.6
Thereafter	143.5		36.0		179.5

^(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 2026.

Asset Retirement Obligations

NSP-Minnesota’s 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
Nuclear	$	1,968.3	$	—	$	—		$	99.5	$	—		$	2,067.8
Wind	104.9		10.3		—			4.8		(6.9		)	113.1
Steam and other production	49.2		—		(3.2		)	1.8		(1.0		)	46.8
Distribution	14.5		—		—			0.6		—			15.1
Miscellaneous	1.8		—		—			—		(1.6		)	0.2
Natural gas
Transmission and distribution	38.2		—		—			1.6		(3.6		)	36.2
Miscellaneous	0.2		—		—			0.1		—			0.3
Common
Miscellaneous	0.8		—		—			—		—			0.8
Total liability	$	2,177.9	$	10.3	$	(3.2	)	$	108.4	$	(13.1	)	$	2,280.3

^(a)  Amounts incurred relate to the wind farms placed in service in 2019 (Lake Benton and Foxtail).

^(b)  Amounts settled related to closure of certain ash containment facilities.

^(c)  In 2019, AROs were revised for changes in timing and estimates of cash flows. Changes in wind AROs were driven by new dismantling studies. Changes in gas transmission and distribution AROs were primarily related to increased gas line mileage and number of services, which were more than offset by decreased inflation rates. Changes in steam and other production AROs primarily related to the cost estimates to remediate ponds at production facilities.

	2018
(Millions  of Dollars)	Jan. 1, 2018		Amounts Settled (a)			Accretion		Cash Flow Revisions  (b)			Dec. 31, 2018  (c)
Electric
Nuclear	$	1,873.6	$	—		$	94.7	$	—		$	1,968.3
Wind	94.1		—			4.3		6.5			104.9
Steam and other production	64.0		(6.6		)	2.1		(10.3		)	49.2
Distribution	5.8		—			0.2		8.5			14.5
Miscellaneous	1.9		—			—		(0.1		)	1.8
Natural gas
Transmission and distribution	43.6		—			1.8		(7.2		)	38.2
Miscellaneous	0.2		—			—		—			0.2
Common
Miscellaneous	0.7		—			0.1		—			0.8
Total liability	$	2,083.9	$	(6.6	)	$	103.2	$	(2.6	)	$	2,177.9

^(a)  Amounts settled related to asbestos abatement projects and closure of certain ash containment facilities.

^(b)  In 2018, AROs were revised for changes in timing and estimates of cash flows. Changes in gas transmission and distribution AROs were mainly related to increased gas line mileage and number of services, which were more than offset by increased discount rates. Changes in electric distribution AROs primarily related to increased labor costs.

^(c) 

There were no ARO amounts incurred in 2018.

Funded Status of Nuclear Decommissioning Obligation

The following amounts were prepared on a regulatory basis and not directly recorded in the financial statements as an ARO.

	Regulatory Basis
(Millions of Dollars)	2019			2018
Estimated decommissioning cost obligation from most recently approved study (in 2014 dollars)	$	3,012.3		$	3,012.3
Effect of escalating costs	688.2			538.9
Estimated decommissioning cost obligation (in current dollars)	3,700.5			3,551.2
Effect of escalating costs to payment date	7,505.0			7,654.3
Estimated future decommissioning costs (undiscounted)	11,205.5			11,205.5
Effect of discounting obligation (using average risk-free interest rate of 2.39% and 3.33% for 2019 and 2018, respectively)	(5,562.2		)	(6,911.5		)
Discounted decommissioning cost obligation	$	5,643.3		$	4,294.0
Assets held in external decommissioning trust	$	2,439.6		$	2,054.7
Underfunding of external decommissioning fund compared to the discounted decommissioning obligation	3,203.7			2,239.3

Reconciliation of Decommissioning Cost Obligation - Regulatory to GAAP

Reconciliation of the discounted decommissioning cost obligation - regulated basis to the ARO recorded in accordance with GAAP:

(Millions of Dollars)	2019			2018
Discounted decommissioning cost obligation - regulated basis	$	5,643.3		$	4,294.0
Differences in discount rate and market risk premium	(2,295.2		)	(1,446.4		)
O&M costs not included for GAAP	(1,280.3		)	(879.3		)
Nuclear production decommissioning ARO - GAAP	$	2,067.8		$	1,968.3

Nuclear Decommissioning Expenses Recognized as Result of Regulation

Decommissioning expenses recognized as a result of regulation:

(Millions of Dollars)	2019		2018		2017
Annual decommissioning recorded as depreciation expense: (a) (b)	$	20.4	$	20.4	$	20.4

^(a)  Decommissioning expense does not include depreciation of the capitalized nuclear asset retirement costs.

^(b) 

Decommissioning expenses in 2019, 2018 and 2017 include Minnesota’s retail jurisdiction annual funding requirement of approximately $14.0 million.