Benefit Plans and Other Postretirement Benefits (Details)
$ in Thousands |
1 Months Ended |
3 Months Ended |
9 Months Ended |
|
Jan. 31, 2017
USD ($)
Plan
|
Sep. 30, 2017
USD ($)
|
Sep. 30, 2016
USD ($)
|
Sep. 30, 2017
USD ($)
|
Sep. 30, 2016
USD ($)
|
| Pension Plan [Member] |
|
|
|
|
|
| Components of Net Periodic Benefit Cost (Credit) [Abstract] |
|
|
|
|
|
| Service cost |
|
$ 2,439
|
$ 2,440
|
$ 7,319
|
$ 7,320
|
| Interest cost |
|
4,928
|
5,315
|
14,783
|
15,945
|
| Expected return on plan assets |
|
(6,971)
|
(6,901)
|
(20,913)
|
(20,703)
|
| Amortization of prior service cost (credit) |
|
0
|
0
|
0
|
0
|
| Amortization of net loss (gain) |
|
3,245
|
2,997
|
9,735
|
8,991
|
| Net periodic benefit cost (credit) |
|
3,641
|
3,851
|
10,924
|
11,553
|
| Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation |
|
553
|
637
|
1,275
|
1,353
|
| Net benefit cost (credit) recognized for financial reporting |
|
4,194
|
4,488
|
12,199
|
12,906
|
| Total contributions to the pension plans during the period |
$ 23,000
|
|
|
|
|
| Pension Plan [Member] | Xcel Energy Inc. |
|
|
|
|
|
| Components of Net Periodic Benefit Cost (Credit) [Abstract] |
|
|
|
|
|
| Total contributions to the pension plans during the period |
$ 150,000
|
|
|
|
|
| Number of Xcel Energy's pension plans to which contributions were made | Plan |
4
|
|
|
|
|
| Other Postretirement Benefits Plan [Member] |
|
|
|
|
|
| Components of Net Periodic Benefit Cost (Credit) [Abstract] |
|
|
|
|
|
| Service cost |
|
219
|
194
|
657
|
582
|
| Interest cost |
|
415
|
455
|
1,245
|
1,365
|
| Expected return on plan assets |
|
(589)
|
(594)
|
(1,767)
|
(1,782)
|
| Amortization of prior service cost (credit) |
|
(100)
|
(100)
|
(300)
|
(300)
|
| Amortization of net loss (gain) |
|
(155)
|
(146)
|
(465)
|
(438)
|
| Net periodic benefit cost (credit) |
|
(210)
|
(191)
|
(630)
|
(573)
|
| Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation |
|
0
|
0
|
0
|
0
|
| Net benefit cost (credit) recognized for financial reporting |
|
$ (210)
|
$ (191)
|
$ (630)
|
$ (573)
|