Benefit Plans and Other Postretirement Benefits, Projected Benefit Payments (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Pension Plans
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2017	$ 28,596
2018	28,086
2019	28,545
2020	29,567
2021	29,716
2022-2026	156,673
Postretirement Benefit Plan
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2017	3,420
2018	3,203
2019	3,008
2020	3,015
2021	3,096
2022-2026	14,135
Expected Medicare Part D Subsidies [Abstract]
2017	24
2018	26
2019	24
2020	25
2021	26
2022-2026	148
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
2017	3,396
2018	3,177
2019	2,984
2020	2,990
2021	3,070
2022-2026	$ 13,987

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No definition available.

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Namespace Prefix:	sps_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in the five fiscal years thereafter (the aggregate net amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

+ References

No definition available.