Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Estimated Minimum Purchases Under Fuel Contracts

The estimated minimum purchases for PSCo under these contracts as of Dec. 31, 2016, are as follows:

(Millions of Dollars)	Coal		Natural gas supply		Natural gas storage and transportation
2017	$	241.2	$	293.6	$	117.8
2018	143.1		185.7		69.0
2019	68.6		179.7		37.1
2020	48.5		184.3		36.6
2021	49.6		191.5		34.4
Thereafter	293.4		171.2		609.9
Total	$	844.4	$	1,206.0	$	904.8

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

At Dec. 31, 2016, the estimated future payments for capacity and energy that PSCo is obligated to purchase pursuant to these executory contracts, subject to availability, are as follows:

(Millions of Dollars)	Capacity		Energy (a)
2017	$	24.3	$	4.4
2018	20.1		—
2019	11.5		—
2020	3.0		—
2021	3.0		—
Thereafter	16.4		—
Total	$	78.3	$	4.4

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

Summary of Property Held Under Capital Leases

Total amortization expenses under capital lease assets were approximately $8.1 million, $8.2 million, and $7.2 million for 2016, 2015 and 2014, respectively. Following is a summary of property held under capital leases:

(Millions of Dollars)	Dec. 31, 2016			Dec. 31, 2015
Gas storage facilities	$	200.5		$	200.5
Gas pipeline	20.7			20.7
Property held under capital leases	221.2			221.2
Accumulated depreciation	(65.3		)	(57.2		)
Total property held under capital leases, net	$	155.9		$	164.0

Future Commitments Under Operating and Capital Leases

Future commitments under operating and capital leases are:

(Millions of Dollars)	Operating Leases		PPA (a) (b) Operating Leases		Total Operating Leases		Capital Leases
2017	$	11.0	$	96.3	$	107.3	$	25.7
2018	10.2		96.6		106.8		25.3
2019	10.3		97.5		107.8		25.1
2020	10.3		98.4		108.7		24.9
2021	9.7		99.4		109.1		23.8
Thereafter	45.2		483.7		528.9		462.7
Total minimum obligation							587.5
Interest component of obligation							(431.6		)
Present value of minimum obligation							$	155.9

^(a)  Amounts do not include PPAs accounted for as executory contracts.

^(b)  PPA operating leases contractually expire through 2032.

Asset Retirement Obligations

A reconciliation of PSCo’s AROs for the years ended Dec. 31, 2016 and 2015 is as follows:

(Thousands of Dollars)	Beginning Balance Jan. 1, 2016		Liabilities Recognized		Accretion		Cash Flow     Revisions (a)			Ending Balance      Dec. 31, 2016 (b)
Electric plant
Steam and other production asbestos	$	38,676	$	—	$	1,877	$	(103	)	$	40,450
Steam and other production ash containment	70,767		—		3,078		(1,245		)	72,600
Wind production	1,992		—		19		61			2,072
Electric distribution	1,130		—		45		6,494			7,669
Other	1,054		214		46		206			1,520
Natural gas plant
Gas transmission and distribution	122,168		—		5,009		33,542			160,719
Other	3,925		—		155		—			4,080
Common and other property
Common miscellaneous	796		—		28		(371		)	453
Total liability	$	240,508	$	214	$	10,257	$	38,584		$	289,563

^(a)  In 2016, AROs were revised for changes in estimated cash flows and the timing of those cash flows. Changes in the gas transmission and distribution AROs were mainly related to increased miles of gas mains.

^(b)  There were no ARO liabilities settled during the year ended Dec. 31, 2016.

(Thousands of Dollars)	Beginning Balance Jan. 1, 2015		Accretion		Cash Flow    Revisions (a)			Ending Balance  Dec. 31, 2015 (b)
Electric plant
Steam and other production asbestos	$	36,856	$	1,820	$	—		$	38,676
Steam and other production ash containment	61,885		2,769		6,113			70,767
Wind production	2,095		18		(121		)	1,992
Electric distribution	1,182		47		(99		)	1,130
Other	1,150		46		(142		)	1,054
Natural gas plant
Gas transmission and distribution	117,474		4,694		—			122,168
Other	3,886		153		(114		)	3,925
Common and other property
Common miscellaneous	768		28		—			796
Total liability	$	225,296	$	9,575	$	5,637		$	240,508

^(a)  In 2015, AROs were revised for changes in estimated cash flows and the timing of those cash flows. Changes in the ash containment ARO were mainly related to the final coal ash rule mentioned above.

^(b)  There were no ARO liabilities recognized or settled during the year ended Dec. 31, 2015.