XML 66 R41.htm IDEA: XBRL DOCUMENT
v3.8.0.1

PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Tables) | 12 Months Ended
--- | ---
Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Fair value measurements of plan assets | The table below categorizes the fair value measurements of the Spire pension plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 37.3 |  |  | $ | — |  |  | $ | — |  |  | $ | 37.3 |
Equity mutual funds - domestic | 42.1 |  |  | 25.4 |  |  | — |  |  | 67.5 |
Equity mutual funds - international | 37.4 |  |  | 11.2 |  |  | — |  |  | 48.6 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | 34.4 |  |  | 68.5 |  |  | — |  |  | 102.9 |
US government | 33.2 |  |  | 4.5 |  |  | — |  |  | 37.7 |
US corporate | 183.7 |  |  | — |  |  | — |  |  | 183.7 |
US municipal | 4.2 |  |  | — |  |  | — |  |  | 4.2 |
International | 45.1 |  |  | 7.2 |  |  | — |  |  | 52.3 |
Derivatives and margin (payable) | (2.6 | ) |  | — |  |  | — |  |  | (2.6 | )
Total | $ | 414.8 |  |  | $ | 116.8 |  |  | $ | — |  |  | $ | 531.6 |
As of September 30, 2016 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 51.2 |  |  | $ | — |  |  | $ | — |  |  | $ | 51.2 |
Stock/bond mutual funds | 99.3 |  |  | 26.7 |  |  | 0.1 |  |  | 126.1 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | 23.0 |  |  | 126.0 |  |  | — |  |  | 149.0 |
US government | 42.1 |  |  | 3.0 |  |  | — |  |  | 45.1 |
US corporate | 137.4 |  |  | — |  |  | — |  |  | 137.4 |
US municipal | 6.3 |  |  | — |  |  | — |  |  | 6.3 |
International | 25.3 |  |  | — |  |  | — |  |  | 25.3 |
Derivatives and margin (payable) | (1.0 | ) |  | 1.1 |  |  | — |  |  | 0.1 |
Total | $ | 383.6 |  |  | $ | 156.8 |  |  | $ | 0.1 |  |  | $ | 540.5 |
The table below categorizes the fair value measurements of Spire’s postretirement plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 4.0 |  |  | $ | — |  |  | $ | — |  |  | $ | 4.0 |
US stock/bond mutual funds | 174.1 |  |  | 71.7 |  |  | — |  |  | 245.8 |
International fund | 1.0 |  |  | 14.7 |  |  | — |  |  | 15.7 |
Total | $ | 179.1 |  |  | $ | 86.4 |  |  | $ | — |  |  | $ | 265.5 |
As of September 30, 2016 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 4.8 |  |  | $ | — |  |  | $ | — |  |  | $ | 4.8 |
US stock/bond mutual funds | 157.9 |  |  | 68.5 |  |  | — |  |  | 226.4 |
International fund | 0.9 |  |  | 14.3 |  |  | — |  |  | 15.2 |
Total | $ | 163.6 |  |  | $ | 82.8 |  |  | $ | — |  |  | $ | 246.4 |
Pension Plans |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Net periodic cost | The net periodic pension costs include the following components:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Service cost – benefits earned during the period | $ | 20.5 |  |  | $ | 15.3 |  |  | $ | 17.3 |  |  | $ | 12.7 |  |  | $ | 10.0 |  |  | $ | 11.5 |  |  | $ | 6.2 |  |  | $ | 5.3 |  |  | $ | 5.8 |
Interest cost on projected benefit obligation | 27.9 |  |  | 28.0 |  |  | 29.5 |  |  | 19.5 |  |  | 21.7 |  |  | 23.3 |  |  | 6.1 |  |  | 6.3 |  |  | 6.2 |
Expected return on plan assets | (38.5 | ) |  | (34.9 | ) |  | (37.4 | ) |  | (28.1 | ) |  | (26.7 | ) |  | (29.2 | ) |  | (7.2 | ) |  | (8.2 | ) |  | (8.2 | )
Amortization of prior service cost | 1.0 |  |  | 0.4 |  |  | 0.5 |  |  | 1.0 |  |  | 0.4 |  |  | 0.5 |  |  | — |  |  | — |  |  | — |
Amortization of actuarial loss | 12.5 |  |  | 8.0 |  |  | 7.5 |  |  | 10.7 |  |  | 7.9 |  |  | 7.5 |  |  | 1.8 |  |  | 0.1 |  |  | — |
Loss on lump-sum settlements and curtailments | 17.9 |  |  | 3.3 |  |  | 19.6 |  |  | 13.5 |  |  | — |  |  | 18.0 |  |  | 4.6 |  |  | 3.3 |  |  | 1.6 |
Special termination benefits | 0.9 |  |  | 1.6 |  |  | — |  |  | — |  |  | 1.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Subtotal | 42.2 |  |  | 21.7 |  |  | 37.0 |  |  | 29.3 |  |  | 14.9 |  |  | 31.6 |  |  | 11.5 |  |  | 6.8 |  |  | 5.4 |
Regulatory adjustment | (2.4 | ) |  | 17.8 |  |  | (2.1 | ) |  | (4.1 | ) |  | 11.7 |  |  | (5.2 | ) |  | 1.8 |  |  | 6.1 |  |  | 3.1 |
Net pension cost | $ | 39.8 |  |  | $ | 39.5 |  |  | $ | 34.9 |  |  | $ | 25.2 |  |  | $ | 26.6 |  |  | $ | 26.4 |  |  | $ | 13.3 |  |  | $ | 12.9 |  |  | $ | 8.5 |
Other changes in plan assets and benefit obligations recognized in other comprehensive income | Other changes in plan assets and pension benefit obligations recognized in other comprehensive income or loss include the following:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Current year actuarial loss | $ | 14.1 |  |  | $ | 46.8 |  |  | $ | 48.3 |  |  | $ | 14.8 |  |  | $ | 21.6 |  |  | $ | 26.0 |  |  | $ | 3.3 |  |  | $ | 25.2 |  |  | $ | 22.3 |
Amortization of actuarial loss | (12.5 | ) |  | (8.0 | ) |  | (7.5 | ) |  | (10.7 | ) |  | (7.9 | ) |  | (7.5 | ) |  | (1.8 | ) |  | (0.1 | ) |  | — |
Acceleration of loss recognized due to settlement | (18.2 | ) |  | (3.3 | ) |  | (19.6 | ) |  | (13.5 | ) |  | — |  |  | (18.0 | ) |  | (4.5 | ) |  | (3.3 | ) |  | (1.6 | )
Current year service cost | — |  |  | 5.0 |  |  | — |  |  | — |  |  | 5.0 |  |  | — |  |  | — |  |  | — |  |  | — |
Current year prior year service cost | (20.7 | ) |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (20.7 | ) |  | — |  |  | — |
Amortization of prior service cost | (1.0 | ) |  | (0.4 | ) |  | (0.5 | ) |  | (1.0 | ) |  | (0.4 | ) |  | (0.5 | ) |  | — |  |  | — |  |  | — |
Subtotal | (38.3 | ) |  | 40.1 |  |  | 20.7 |  |  | (10.4 | ) |  | 18.3 |  |  | — |  |  | (23.7 | ) |  | 21.8 |  |  | 20.7 |
Regulatory adjustment | 38.0 |  |  | (39.8 | ) |  | (21.2 | ) |  | 10.1 |  |  | (18.0 | ) |  | (0.5 | ) |  | 23.7 |  |  | (21.8 | ) |  | (20.7 | )
Total recognized in OCI | $ | (0.3 | ) |  | $ | 0.3 |  |  | $ | (0.5 | ) |  | $ | (0.3 | ) |  | $ | 0.3 |  |  | $ | (0.5 | ) |  | $ | — |  |  | $ | — |  |  | $ | — |
Reconciliation of the beginning and ending balances of benefit obligation | The following table shows the reconciliation of the beginning and ending balances of the pension benefit obligation at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Benefit obligation, beginning of year | $ | 794.7 |  |  | $ | 652.3 |  |  | $ | 560.0 |  |  | $ | 497.6 |  |  | $ | 174.3 |  |  | $ | 154.7 |
Service cost | 20.5 |  |  | 15.3 |  |  | 12.7 |  |  | 10.0 |  |  | 6.2 |  |  | 5.3 |
Interest cost | 27.9 |  |  | 28.0 |  |  | 19.5 |  |  | 21.7 |  |  | 6.1 |  |  | 6.3 |
Actuarial (gain) loss | (0.9 | ) |  | 85.8 |  |  | (0.5 | ) |  | 59.2 |  |  | 1.6 |  |  | 26.6 |
Plan amendments | (20.7 | ) |  | 5.1 |  |  | — |  |  | 5.1 |  |  | (20.7 | ) |  | — |
Spire EnergySouth acquisition | — |  |  | 60.4 |  |  | — |  |  | — |  |  | — |  |  | — |
Settlement loss | 14.6 |  |  | 1.1 |  |  | 12.2 |  |  | — |  |  | 2.4 |  |  | 1.1 |
Special termination benefits | 0.9 |  |  | 1.6 |  |  | — |  |  | 1.6 |  |  | — |  |  | — |
Settlement benefits paid | (62.2 | ) |  | (16.6 | ) |  | (43.5 | ) |  | — |  |  | (18.7 | ) |  | (16.6 | )
Regular benefits paid | (26.0 | ) |  | (38.3 | ) |  | (20.8 | ) |  | (35.2 | ) |  | (3.0 | ) |  | (3.1 | )
Benefit obligation, end of year | $ | 748.8 |  |  | $ | 794.7 |  |  | $ | 539.6 |  |  | $ | 560.0 |  |  | $ | 148.2 |  |  | $ | 174.3 |
Accumulated benefit obligation, end of year | $ | 701.4 |  |  | $ | 724.5 |  |  | $ | 500.4 |  |  | $ | 517.7 |  |  | $ | 142.8 |  |  | $ | 149.8 |
Fair value of plan assets | The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Fair value of plan assets, beginning of year | $ | 540.5 |  |  | $ | 448.9 |  |  | $ | 395.7 |  |  | $ | 339.9 |  |  | $ | 100.0 |  |  | $ | 109.0 |
Actual return on plan assets | 38.0 |  |  | 75.1 |  |  | 25.1 |  |  | 64.4 |  |  | 7.7 |  |  | 10.7 |
Employer contributions | 41.3 |  |  | 26.6 |  |  | 29.4 |  |  | 26.6 |  |  | 11.9 |  |  | — |
Spire EnergySouth acquisition | — |  |  | 44.8 |  |  | — |  |  | — |  |  | — |  |  | — |
Settlement benefits paid | (62.2 | ) |  | (16.6 | ) |  | (43.5 | ) |  | — |  |  | (18.7 | ) |  | (16.6 | )
Regular benefits paid | (26.0 | ) |  | (38.3 | ) |  | (20.8 | ) |  | (35.2 | ) |  | (3.0 | ) |  | (3.1 | )
Fair value of plan assets, end of year | $ | 531.6 |  |  | $ | 540.5 |  |  | $ | 385.9 |  |  | $ | 395.7 |  |  | $ | 97.9 |  |  | $ | 100.0 |
Funded status of plans, end of year | $ | (217.2 | ) |  | $ | (254.2 | ) |  | $ | (153.7 | ) |  | $ | (164.3 | ) |  | $ | (50.3 | ) |  | $ | (74.3 | )
Amounts recognized in consolidated balance sheets | The following table sets forth the amounts recognized in the balance sheets at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Current liabilities | $ | (0.5 | ) |  | $ | (0.6 | ) |  | $ | (0.5 | ) |  | $ | (0.6 | ) |  | $ | — |  |  | $ | — |
Noncurrent liabilities | (216.7 | ) |  | (253.6 | ) |  | (153.2 | ) |  | (163.7 | ) |  | (50.3 | ) |  | (74.3 | )
Total | $ | (217.2 | ) |  | $ | (254.2 | ) |  | $ | (153.7 | ) |  | $ | (164.3 | ) |  | $ | (50.3 | ) |  | $ | (74.3 | )
Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic pension cost consist of:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Net actuarial loss | $ | 163.0 |  |  | $ | 179.4 |  |  | $ | 126.2 |  |  | $ | 135.5 |  |  | $ | 40.9 |  |  | $ | 43.9 |
Prior service (credit) cost | (13.4 | ) |  | 8.2 |  |  | 7.3 |  |  | 8.2 |  |  | (20.7 | ) |  | — |
Subtotal | 149.6 |  |  | 187.6 |  |  | 133.5 |  |  | 143.7 |  |  | 20.2 |  |  | 43.9 |
Adjustments for amounts included in regulatory assets | (147.1 | ) |  | (184.8 | ) |  | (131.0 | ) |  | (140.9 | ) |  | (20.2 | ) |  | (43.9 | )
Total | $ | 2.5 |  |  | $ | 2.8 |  |  | $ | 2.5 |  |  | $ | 2.8 |  |  | $ | — |  |  | $ | — |
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost | At September 30, 2017, the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic pension cost during fiscal 2018:
| Spire |  | Spire Missouri |  | Spire Alabama
Amortization of net actuarial loss | $ | 12.6 |  |  | $ | 10.5 |  |  | $ | 2.1 |
Amortization of prior service (credit) cost | (0.9 | ) |  | 0.9 |  |  | (1.8 | )
Subtotal | 11.7 |  |  | 11.4 |  |  | 0.3 |
Regulatory adjustment | (11.4 | ) |  | (11.1 | ) |  | (0.3 | )
Total | $ | 0.3 |  |  | $ | 0.3 |  |  | $ | — |
Assumptions used to calculate net periodic cost and benefit obligations. | The assumptions used to calculate the benefit obligations are as follows:
| 2017 |  | 2016
Weighted average discount rate - Spire Missouri East plans | 3.75% |  | 3.50%
Weighted average discount rate - Spire Missouri West plans | 3.70% |  | 3.50%
Weighted average discount rate - Spire Alabama plans | 3.65%/3.70% |  | 3.45%/3.50%
Weighted average rate of future compensation increase | 3.00% |  | 3.00%
The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows:
| 2017 |  | 2016 |  | 2015
Weighted average discount rate - Spire Missouri East plans | 3.50% |  | 4.40% |  | 4.30%
Weighted average discount rate - Spire Missouri West plans | 3.50% |  | 4.50% |  | 4.45%
Weighted average rate of future compensation increase | 3.00% |  | 3.00% |  | 3.00%
Expected long-term rate of return on plan assets | 7.75% |  | 7.75% |  | 7.75%
The assumptions used to calculate net periodic pension costs for Spire Alabama are as follows:
| 2017 |  | 2016 |  | 2015
Weighted average discount rate | 3.45%/3.50% |  | 4.25%/4.30% |  | 4.15%/4.25%
Weighted average rate of future compensation increase | 3.00% |  | 3.00% |  | 2.92%
Expected long-term rate of return on plan assets | 7.25% |  | 7.50% |  | 7.00%/7.25%
Projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have projected benefit obligation and accumulated benefit obligation in excess of plan assets | Following are the year-end projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have a projected benefit obligation and an accumulated benefit obligation in excess of plan assets:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Projected benefit obligation | $ | 748.8 |  |  | $ | 794.7 |  |  | $ | 539.6 |  |  | $ | 560.0 |  |  | $ | 148.2 |  |  | $ | 174.3 |
Accumulated benefit obligation | 701.4 |  |  | 724.5 |  |  | 500.4 |  |  | 517.7 |  |  | 142.8 |  |  | 149.8 |
Fair value of plan assets | 531.6 |  |  | 540.5 |  |  | 385.9 |  |  | 395.7 |  |  | 97.9 |  |  | 100.0 |
Targeted and actual plan assets by category | Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama:
Spire Missouri | 2017 Target |  | 2017 Actual |  | 2016 Target |  | 2016 Actual
Equity markets | 56.4 | % |  | 56.8 | % |  | 56.2 | % |  | 56.9 | %
Debt securities | 43.6 | % |  | 42.0 | % |  | 43.8 | % |  | 43.1 | %
Cash equivalents | — | % |  | 1.2 | % |  | — | % |  | — | %
Total | 100.0 | % |  | 100.0 | % |  | 100.0 | % |  | 100.0 | %
Spire Alabama | 2017 Target |  | 2017 Actual |  | 2016 Target |  | 2016 Actual
Equity markets | 60.0 | % |  | 58.5 | % |  | 60.0 | % |  | 59.2 | %
Debt securities | 29.0 | % |  | 28.7 | % |  | 29.0 | % |  | 28.8 | %
Other* | 11.0 | % |  | 12.8 | % |  | 11.0 | % |  | 12.0 | %
Total | 100.0 | % |  | 100.0 | % |  | 100.0 | % |  | 100.0 | %
* | Includes cash and funds invested in real estate, commodities, natural resources and inflation-protected securities.
Expected benefit payments for the succeeding five fiscal years | Following are expected pension benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter, for Spire, Spire Missouri, and Spire Alabama:
| 2018 |  | 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023- 2027
Spire | $ | 63.5 |  |  | $ | 63.2 |  |  | $ | 63.2 |  |  | $ | 58.1 |  |  | $ | 57.9 |  |  | $ | 281.1 |
Spire Missouri | 50.7 |  |  | 49.5 |  |  | 49.1 |  |  | 43.5 |  |  | 42.1 |  |  | 198.1 |
Spire Alabama | 10.3 |  |  | 11.1 |  |  | 11.5 |  |  | 11.9 |  |  | 13.0 |  |  | 67.8 |
Postretirement Plans |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Net periodic cost | Net periodic postretirement benefit costs consist of the following components:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Service cost – benefits earned during the period | $ | 11.0 |  |  | $ | 10.9 |  |  | $ | 12.8 |  |  | $ | 10.4 |  |  | $ | 10.6 |  |  | $ | 12.3 |  |  | $ | 0.3 |  |  | $ | 0.3 |  |  | $ | 0.5 |
Interest cost on accumulated postretirement benefit obligation | 8.6 |  |  | 10.2 |  |  | 11.2 |  |  | 6.8 |  |  | 8.1 |  |  | 8.6 |  |  | 1.6 |  |  | 2.1 |  |  | 2.6 |
Expected return on plan assets | (13.6 | ) |  | (13.5 | ) |  | (13.2 | ) |  | (9.0 | ) |  | (8.5 | ) |  | (8.1 | ) |  | (4.4 | ) |  | (5.0 | ) |  | (5.1 | )
Amortization of prior service cost (credit) | — |  |  | 0.3 |  |  | 0.8 |  |  | 0.2 |  |  | 0.3 |  |  | 0.8 |  |  | (0.2 | ) |  | — |  |  | — |
Amortization of actuarial loss (gain) | 2.5 |  |  | 3.6 |  |  | 5.1 |  |  | 2.6 |  |  | 3.8 |  |  | 5.1 |  |  | (0.1 | ) |  | (0.2 | ) |  | — |
Special termination benefits | — |  |  | 2.6 |  |  | — |  |  | — |  |  | 2.6 |  |  | — |  |  | — |  |  | — |  |  | — |
Subtotal | 8.5 |  |  | 14.1 |  |  | 16.7 |  |  | 11.0 |  |  | 16.9 |  |  | 18.7 |  |  | (2.8 | ) |  | (2.8 | ) |  | (2.0 | )
Regulatory adjustment | (3.2 | ) |  | (6.6 | ) |  | (11.0 | ) |  | (1.5 | ) |  | (4.8 | ) |  | (9.2 | ) |  | (1.8 | ) |  | (1.8 | ) |  | (1.8 | )
Net postretirement benefit cost | $ | 5.3 |  |  | $ | 7.5 |  |  | $ | 5.7 |  |  | $ | 9.5 |  |  | $ | 12.1 |  |  | $ | 9.5 |  |  | $ | (4.6 | ) |  | $ | (4.6 | ) |  | $ | (3.8 | )
Other changes in plan assets and benefit obligations recognized in other comprehensive income | Other changes in plan assets and postretirement benefit obligations recognized in OCI include the following:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015 |  | 2017 |  | 2016 |  | 2015
Current year actuarial (gain) loss | $ | (34.1 | ) |  | $ | 0.8 |  |  | $ | (8.5 | ) |  | $ | (28.5 | ) |  | $ | 1.4 |  |  | $ | (2.4 | ) |  | $ | (4.5 | ) |  | $ | (0.6 | ) |  | $ | (6.1 | )
Amortization of actuarial (loss) gain | (2.5 | ) |  | (3.6 | ) |  | (5.1 | ) |  | (2.6 | ) |  | (3.8 | ) |  | (5.1 | ) |  | 0.1 |  |  | 0.2 |  |  | — |
Current year prior service credit | (1.4 | ) |  | (1.8 | ) |  | (4.9 | ) |  | — |  |  | — |  |  | (4.9 | ) |  | (1.4 | ) |  | (1.8 | ) |  | — |
Amortization of prior service (cost) credit | — |  |  | (0.3 | ) |  | (0.8 | ) |  | (0.2 | ) |  | (0.3 | ) |  | (0.8 | ) |  | 0.2 |  |  | — |  |  | — |
Subtotal | (38.0 | ) |  | (4.9 | ) |  | (19.3 | ) |  | (31.3 | ) |  | (2.7 | ) |  | (13.2 | ) |  | (5.6 | ) |  | (2.2 | ) |  | (6.1 | )
Regulatory adjustment | 38.0 |  |  | 4.9 |  |  | 19.3 |  |  | 31.3 |  |  | 2.7 |  |  | 13.2 |  |  | 5.6 |  |  | 2.2 |  |  | 6.1 |
Total recognized in OCI | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Reconciliation of the beginning and ending balances of benefit obligation | The following table sets forth the reconciliation of the beginning and ending balances of the postretirement benefit obligation at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Benefit obligation, beginning of year | $ | 259.2 |  |  | $ | 239.2 |  |  | $ | 207.9 |  |  | $ | 191.9 |  |  | $ | 45.4 |  |  | $ | 47.3 |
Service cost | 11.0 |  |  | 10.9 |  |  | 10.4 |  |  | 10.6 |  |  | 0.3 |  |  | 0.3 |
Interest cost | 8.6 |  |  | 10.2 |  |  | 6.8 |  |  | 8.1 |  |  | 1.6 |  |  | 2.1 |
Actuarial (gain) loss | (22.1 | ) |  | 7.1 |  |  | (20.9 | ) |  | 6.7 |  |  | — |  |  | 0.4 |
Plan amendments | (1.4 | ) |  | (1.8 | ) |  | — |  |  | — |  |  | (1.4 | ) |  | (1.8 | )
Spire EnergySouth acquisition | — |  |  | 5.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Special termination benefits | — |  |  | 2.6 |  |  | — |  |  | 2.6 |  |  | — |  |  | — |
Curtailments | 0.4 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Retiree drug subsidy program | 0.3 |  |  | 0.2 |  |  | 0.3 |  |  | — |  |  | — |  |  | 0.2 |
Gross benefits paid | (17.5 | ) |  | (15.1 | ) |  | (12.0 | ) |  | (12.0 | ) |  | (5.3 | ) |  | (3.1 | )
Benefit obligation, end of year | $ | 238.5 |  |  | $ | 259.2 |  |  | $ | 192.5 |  |  | $ | 207.9 |  |  | $ | 40.6 |  |  | $ | 45.4 |
Fair value of plan assets | The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Fair value of plan assets at beginning of year | $ | 246.4 |  |  | $ | 223.3 |  |  | $ | 159.7 |  |  | $ | 143.6 |  |  | $ | 82.8 |  |  | $ | 79.7 |
Actual return on plan assets | 26.2 |  |  | 19.9 |  |  | 16.8 |  |  | 13.8 |  |  | 8.9 |  |  | 6.2 |
Employer contributions | 10.4 |  |  | 14.3 |  |  | 10.4 |  |  | 14.3 |  |  | — |  |  | — |
Spire EnergySouth acquisition | — |  |  | 4.0 |  |  | — |  |  | — |  |  | — |  |  | — |
Gross benefits paid | (17.5 | ) |  | (15.1 | ) |  | (12.0 | ) |  | (12.0 | ) |  | (5.3 | ) |  | (3.1 | )
Fair value of plan assets, end of year | $ | 265.5 |  |  | $ | 246.4 |  |  | $ | 174.9 |  |  | $ | 159.7 |  |  | $ | 86.4 |  |  | $ | 82.8 |
Funded status of plans, end of year | $ | 27.0 |  |  | $ | (12.8 | ) |  | $ | (17.6 | ) |  | $ | (48.2 | ) |  | $ | 45.8 |  |  | $ | 37.4 |
Amounts recognized in consolidated balance sheets | The following table sets forth the amounts recognized in the balance sheets at September 30:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Current assets | $ | 1.4 |  |  | $ | 0.3 |  |  | $ | 1.4 |  |  | $ | 0.3 |  |  | $ | — |  |  | $ | — |
Noncurrent assets | 47.0 |  |  | 37.4 |  |  | 1.2 |  |  | — |  |  | 45.8 |  |  | 37.4 |
Current liabilities | (0.4 | ) |  | (0.4 | ) |  | (0.4 | ) |  | (0.4 | ) |  | — |  |  | — |
Noncurrent liabilities | (21.0 | ) |  | (50.1 | ) |  | (19.8 | ) |  | (48.1 | ) |  | — |  |  | — |
Total | $ | 27.0 |  |  | $ | (12.8 | ) |  | $ | (17.6 | ) |  | $ | (48.2 | ) |  | $ | 45.8 |  |  | $ | 37.4 |
Pre-tax amounts recognized in accumulated other comprehensive loss not yet recognized as components of net periodic postretirement benefit cost consist of:
| Spire |  | Spire Missouri |  | Spire Alabama
| 2017 |  | 2016 |  | 2017 |  | 2016 |  | 2017 |  | 2016
Net actuarial loss (gain) | $ | 1.5 |  |  | $ | 38.0 |  |  | $ | 12.3 |  |  | $ | 43.4 |  |  | $ | (9.7 | ) |  | $ | (5.4 | )
Prior service credit | (6.6 | ) |  | (5.2 | ) |  | (3.7 | ) |  | (3.4 | ) |  | (2.9 | ) |  | (1.8 | )
Subtotal | (5.1 | ) |  | 32.8 |  |  | 8.6 |  |  | 40.0 |  |  | (12.6 | ) |  | (7.2 | )
Adjustments for amounts included in regulatory assets | 5.1 |  |  | (32.8 | ) |  | (8.6 | ) |  | (40.0 | ) |  | 12.6 |  |  | 7.2 |
Total | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Pre-tax amounts amortized from accumulated other comprehensive income into net periodic cost | At September 30, 2017, the following pre-tax amounts are expected to be amortized from accumulated other comprehensive loss into net periodic postretirement benefit cost during fiscal 2018:
| Spire |  | Spire Missouri |  | Spire Alabama
Amortization of net actuarial loss | $ | 0.9 |  |  | $ | 0.9 |  |  | $ | — |
Amortization of prior service (credit) cost | (0.1 | ) |  | 0.3 |  |  | (0.4 | )
Subtotal | 0.8 |  |  | 1.2 |  |  | (0.4 | )
Regulatory adjustment | (0.8 | ) |  | (1.2 | ) |  | 0.4 |
Total | $ | — |  |  | $ | — |  |  | $ | — |
Assumptions used to calculate net periodic cost and benefit obligations. | The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows:
| 2017 |  | 2016 |  | 2015
Weighted average discount rate - Spire Missouri East plans | 3.15% |  | 4.00% |  | 4.15%
Weighted average discount rate - Spire Missouri West plans | 3.45% |  | 4.30% |  | 4.40%
Weighted average rate of future compensation increase | 3.00% |  | 3.00% |  | 3.00%
Expected long-term rate of return on plan assets - Spire Missouri East plans | 5.75%/7.75% |  | 6.00%/7.75% |  | 6.25%/7.75%
Expected long-term rate of return on plan assets - Spire Missouri West plans | 5.50% |  | 4.75% |  | 5.00%
The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows:
| 2017 |  | 2016 |  | 2015
Weighted average discount rate | 3.60% |  | 4.50% |  | 4.40%
Expected long-term rate of return on plan assets | 4.00%/6.25% |  | 4.50%/7.25% |  | 4.75%/7.50%
The assumptions used to calculate the accumulated postretirement benefit obligations are as follows:
| 2017 |  | 2016
Weighted average discount rate - Spire Alabama plans | 3.80% |  | 3.60%
Weighted average discount rate - Spire Missouri East plans | 3.60% |  | 3.15%
Weighted average discount rate - Spire Missouri West plans | 3.60% |  | 3.45%
Weighted average rate of future compensation increase - Spire Missouri East plans | 3.00% |  | 3.00%
Targeted and actual plan assets by category | Following are the targeted and actual plan assets by category as of September 30 of each year for Spire Missouri and Spire Alabama:
Spire Missouri | Target |  | 2017 Actual |  | 2016 Actual
Equity securities | 60.0 | % |  | 59.0 | % |  | 59.1 | %
Debt securities | 40.0 | % |  | 39.4 | % |  | 39.4 | %
Other (cash and cash equivalents held to make benefit payments) | — | % |  | 1.6 | % |  | 1.5 | %
Total | 100.0 | % |  | 100.0 | % |  | 100.0 | %
Spire Alabama | Target |  | 2017 Actual |  | 2016 Actual
Equity securities | 60.0 | % |  | 60.1 | % |  | 60.5 | %
Debt securities | 40.0 | % |  | 39.9 | % |  | 39.5 | %
Total | 100.0 | % |  | 100.0 | % |  | 100.0 | %
Expected benefit payments for the succeeding five fiscal years | Following are expected postretirement benefit payments for the succeeding five fiscal years, and in aggregate for the five fiscal years thereafter for Spire, Spire Missouri, and Spire Alabama:
| 2018 |  | 2019 |  | 2020 |  | 2021 |  | 2022 |  | 2023- 2027
Spire | $ | 15.0 |  |  | $ | 16.0 |  |  | $ | 17.1 |  |  | $ | 18.3 |  |  | $ | 18.9 |  |  | $ | 101.3 |
Spire Missouri | 11.8 |  |  | 12.8 |  |  | 14.0 |  |  | 15.2 |  |  | 15.9 |  |  | 86.5 |
Spire Alabama | 2.8 |  |  | 2.8 |  |  | 2.8 |  |  | 2.8 |  |  | 2.7 |  |  | 13.0 |
Assumed medical cost trend rates and effect of an assumed 1% changed in assumed medical cost trend. | The assumed medical cost trend rates at September 30 are as follows:
| 2017 |  | 2016
Medical cost trend assumed for next year - Spire Missouri | 7.25% |  | 7.50%
Medical cost trend assumed for next year - Spire Alabama | 7.25% |  | 7.50%
Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate) | 5.00% |  | 5.00%
Year the rate reaches the ultimate trend | 2023 |  | 2023
The following table presents the effects of an assumed 1% change in the assumed medical cost trend rate:
| Spire |  | Spire Missouri |  | Spire Alabama
| 1% Increase |  | 1% Decrease |  | 1% Increase |  | 1% Decrease |  | 1% Increase |  | 1% Decrease
Net periodic postretirement benefit cost | $ | 1.7 |  |  | $ | (1.4 | ) |  | $ | 1.6 |  |  | $ | (1.3 | ) |  | $ | 0.1 |  |  | $ | (0.1 | )
Accumulated postretirement benefit obligation | 10.0 |  |  | (9.2 | ) |  | 8.0 |  |  | (7.4 | ) |  | 1.4 |  |  | (1.3 | )
Spire Missouri |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |
Fair value measurements of plan assets | The table below categorizes the fair value measurements of Spire Alabama’s pension plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 3.4 |  |  | $ | — |  |  | $ | — |  |  | $ | 3.4 |
Equity mutual funds - domestic | 28.4 |  |  | 9.1 |  |  | — |  |  | 37.5 |
Equity mutual funds - international | 25.2 |  |  | 3.7 |  |  | — |  |  | 28.9 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | 23.2 |  |  | — |  |  | — |  |  | 23.2 |
International | — |  |  | 4.9 |  |  | — |  |  | 4.9 |
Total | $ | 80.2 |  |  | $ | 17.7 |  |  | $ | — |  |  | $ | 97.9 |
As of September 30, 2016 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 0.4 |  |  | $ | — |  |  | $ | — |  |  | $ | 0.4 |
Stock/bond mutual funds | 59.0 |  |  | 11.9 |  |  | — |  |  | 70.9 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | 23.0 |  |  | 5.7 |  |  | — |  |  | 28.7 |
Total | $ | 82.4 |  |  | $ | 17.6 |  |  | $ | — |  |  | $ | 100.0 |
The table below categorizes the fair value measurements of Spire Alabama’s postretirement plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
US stock/bond mutual funds | $ | — |  |  | $ | 71.7 |  |  | $ | — |  |  | $ | 71.7 |
International fund | — |  |  | 14.7 |  |  | — |  |  | 14.7 |
Total | $ | — |  |  | $ | 86.4 |  |  | $ | — |  |  | $ | 86.4 |
As of September 30, 2016 |  |  |  |  |  |  |
US stock/bond mutual funds | $ | — |  |  | $ | 68.5 |  |  | $ | — |  |  | $ | 68.5 |
International fund | — |  |  | 14.3 |  |  | — |  |  | 14.3 |
Total | $ | — |  |  | $ | 82.8 |  |  | $ | — |  |  | $ | 82.8 |
The table below categorizes the fair value measurements of Spire Missouri’s pension plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 31.7 |  |  | $ | — |  |  | $ | — |  |  | $ | 31.7 |
Equity mutual funds - domestic | — |  |  | 11.9 |  |  | — |  |  | 11.9 |
Equity mutual funds - international | — |  |  | 5.7 |  |  | — |  |  | 5.7 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | — |  |  | 68.5 |  |  | — |  |  | 68.5 |
US government | 33.2 |  |  | 4.5 |  |  | — |  |  | 37.7 |
US corporate | 183.7 |  |  | — |  |  | — |  |  | 183.7 |
US municipal | 4.2 |  |  | — |  |  | — |  |  | 4.2 |
International | 45.1 |  |  | — |  |  | — |  |  | 45.1 |
Derivatives and margin (payable) | (2.6 | ) |  | — |  |  | — |  |  | (2.6 | )
Total | $ | 295.3 |  |  | $ | 90.6 |  |  | $ | — |  |  | $ | 385.9 |
As of September 30, 2016 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 46.5 |  |  | $ | — |  |  | $ | — |  |  | $ | 46.5 |
Stock/bond mutual funds | — |  |  | 14.8 |  |  | 0.1 |  |  | 14.9 |
Debt securities: |  |  |  |  |  |  |
US bond mutual funds | — |  |  | 120.2 |  |  | — |  |  | 120.2 |
US government | 42.1 |  |  | 3.0 |  |  | — |  |  | 45.1 |
US corporate | 137.4 |  |  | — |  |  | — |  |  | 137.4 |
US municipal | 6.3 |  |  | — |  |  | — |  |  | 6.3 |
International | 25.2 |  |  | — |  |  | — |  |  | 25.2 |
Derivatives and margin (payable) | (1.0 | ) |  | 1.1 |  |  | — |  |  | 0.1 |
Total | $ | 256.5 |  |  | $ | 139.1 |  |  | $ | 0.1 |  |  | $ | 395.7 |
The table below categorizes the fair value measurements of Spire Missouri’s postretirement plan assets:
| Quoted Prices in Active Markets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total
As of September 30, 2017 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 3.9 |  |  | $ | — |  |  | $ | — |  |  | $ | 3.9 |
US stock/bond mutual funds | 171.0 |  |  | — |  |  | — |  |  | 171.0 |
Total | $ | 174.9 |  |  | $ | — |  |  | $ | — |  |  | $ | 174.9 |
As of September 30, 2016 |  |  |  |  |  |  |
Cash and cash equivalents | $ | 4.6 |  |  | $ | — |  |  | $ | — |  |  | $ | 4.6 |
US stock/bond mutual funds | 155.1 |  |  | — |  |  | — |  |  | 155.1 |
Total | $ | 159.7 |  |  | $ | — |  |  | $ | — |  |  | $ | 159.7 |

X
- Definition Tabular disclosure of fair value measurement of plan assets. + References No definition available. + Details
Name: | lg_FairvaluemeasurementsofplanassetsTableTextBlock
Namespace Prefix: | lg_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefit obligations including accumulated benefit obligation and projected benefit obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAllocationOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amounts related to pension plans and/or other employee benefit plans in accumulated other comprehensive income (loss) expected to be recognized as components of net periodic benefit cost over the next fiscal year, including the net gain (loss), net prior service cost or credit, and net transition asset or obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (s) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAmountsInAccumulatedOtherComprehensiveIncomeLossToBeRecognizedOverNextFiscalYearTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amounts that are recognized in the balance sheet (or statement of financial position) for pension plans and/or other employee benefit plans, showing separately the assets and current and noncurrent liabilities (if applicable) recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAmountsRecognizedInBalanceSheetTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the net gain (loss) and net prior service cost or credit recognized in other comprehensive income (loss) for the period for pension plans and/or other employee benefit plans, and reclassification adjustments of other comprehensive income (loss) for the period, as those amounts, including amortization of the net transition asset or obligation, are recognized as components of net periodic benefit cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAmountsRecognizedInOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the assumptions used to determine for pension plans and/or other employee benefit plans the benefit obligation and net benefit cost, including assumed discount rates, rate increase in compensation increase, and expected long-term rates of return on plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAssumptionsUsedTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the aggregate benefit obligation and aggregate fair value of plan assets for pension plans and/or other employee benefit plans with benefit obligations in excess of plan assets as of the measurement date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920 + Details
Name: | us-gaap_ScheduleOfBenefitObligationsInExcessOfFairValueOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the reconciliation of beginning and ending balances of the fair value of plan assets of pension plans and/or other employee benefit plans showing separately, if applicable, the effects during the period attributable to each of the following: actual return on plan assets, foreign currency exchange rate changes, contributions by the employer, contributions by plan participants, benefits paid, business combinations, divestitures, and settlements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfChangesInFairValueOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the effect of a one-percentage-point increase and the effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs and the accumulated postretirement benefit obligation for health care benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfEffectOfOnePercentagePointChangeInAssumedHealthCareCostTrendRatesTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfExpectedBenefitPaymentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetBenefitCostsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lg_SpireMissouriMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |