Pay vs Performance Disclosure

3 Months Ended

9 Months Ended

12 Months Ended

Dec. 31, 2023

Sep. 30, 2021

Sep. 30, 2024

Jun. 30, 2021

Sep. 30, 2024

USD ($)

$ / shares

Sep. 30, 2023

USD ($)

$ / shares

Sep. 30, 2022

USD ($)

$ / shares

Sep. 30, 2021

USD ($)

$ / shares

Pay vs Performance Disclosure

Company Selected Measure Name

Adjusted EPS

Named Executive Officers, Footnote

(1) Mr. Longhi became our principal executive officer (“PEO”) on December 12, 2023 and was our PEO for the remainder of Fiscal 2024. Mr. Perreault, our former PEO, served as PEO from June 26, 2021 through December 12, 2023. Mr. Walsh, our former PEO, retired on June 26, 2021. Our non-PEO NEOs included: (a) for Fiscal 2024, Messrs. O’Brien, Beard and Koerwer and Mses. Zagorski and Shea-Ballay; (b) for Fiscal 2023, Messrs. O’Brien, Jastrzebski, Beard and Koerwer and Mses. Zagorski and Gaudiosi; (c) for Fiscal 2022, Messrs. Jastrzebski and Beard and Mses. Zagorski and Gaudiosi; and (d) for Fiscal 2021, Messrs. Jastrzebski, Beard and Gallagher and Mses. Zagorski and Gaudiosi.

Peer Group Issuers, Footnote

(3) The Peer Group for which Total Shareholder Return is provided in column (g) is the S&P 500 Utilities Index.

Adjustment To PEO Compensation, Footnote

(2) The following amounts were deducted from/added to Summary Compensation Table total compensation in accordance with the SEC-mandated adjustments to calculate Compensation Actually Paid (“CAP”) to our PEO and average CAP to our non-PEO named executive officers. The fair value of equity awards was determined using methodologies and assumptions developed in a manner substantively consistent with those used to determine the grant date fair value of such awards.

PEO (M. Longhi) Summary Compensation Table Total to CAP Reconciliation
Fiscal Year	2021		2022		2023		2024
Summary Compensation Table Total		n/a		n/a		n/a	$	6,227,806
Deduct Change in Actuarial Present Value of Pension Plans Reported in Fiscal Year		—		—		—		—
Add Service Cost of Pension in Fiscal Year		—		—		—		—
Add Prior Service Cost of Pension in Fiscal Year		—		—		—		—
Deduct Grant Date Fair Value of Stock Awards Granted in Fiscal Year		—		—		—		(3,039,803)
Add-Deduct Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Awards Granted in Fiscal Year		—		—		—		2,830,513
Add-Deduct Change in Fair Value of Outstanding and Unvested Stock Awards Granted in Prior Fiscal Years		—		—		—		—
Add-Deduct Fair Value at Vesting of Stock Awards Granted in Fiscal Year That Vested During Fiscal Year		—		—		—		—
Add-Deduct Change in Fair Value as of Vesting Date of Stock Awards Granted in Prior Fiscal Years For Which Applicable Vesting Conditions Were Satisfied During Fiscal Year		—		—		—		—
Deduct Fair Value as of Prior Fiscal Year-End of Stock Awards Granted in Prior Fiscal Years That Failed to Meet Applicable Vesting Conditions During Fiscal Year		—		—		—		—
Add Dividends or Other Earnings Paid on Stock Awards in the Fiscal Year Prior to the Vesting Date that are not otherwise included in the Total Compensation for the Fiscal Year		—		—		—		171,958
Compensation Actually Paid	$	n/a	$	n/a	$	n/a	$	6,190,474

Former PEO (R. Perreault) Summary Compensation Table Total to CAP Reconciliation
Fiscal Year	2021		2022			2023		2024
Summary Compensation Table Total	$	4,107,789	$	6,060,694	$	9,960,170	$	5,346,550
Deduct Change in Actuarial Present Value of Pension Plans Reported in Fiscal Year		—		—		—		—
Add Service Cost of Pension in Fiscal Year		—		—		—		—
Add Prior Service Cost of Pension in Fiscal Year		—		—		—		—
Deduct Grant Date Fair Value of Stock Awards Granted in Fiscal Year		(2,522,588)		(4,158,984)		(7,733,691)		—
Add-Deduct Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Awards Granted in Fiscal Year		2,855,539		1,999,801		1,454,565		—
Add-Deduct Change in Fair Value of Outstanding and Unvested Stock Awards Granted in Prior Fiscal Years		745,506		(2,073,984)		(1,912,144)		—
Add-Deduct Fair Value at Vesting of Stock Awards Granted in Fiscal Year That Vested During Fiscal Year		—		—		—		—
Add-Deduct Change in Fair Value as of Vesting Date of Stock Awards Granted in Prior Fiscal Years For Which Applicable Vesting Conditions Were Satisfied During Fiscal Year		48,425		151,830		168,939		—
Deduct Fair Value as of Prior Fiscal Year-End of Stock Awards Granted in Prior Fiscal Years That Failed to Meet Applicable Vesting Conditions During Fiscal Year		(4,165)		(13,838)		(36,180)		(2,517,804)
Add Dividends or Other Earnings Paid on Stock Awards in the Fiscal Year Prior to the Vesting Date that are not otherwise included in the Total Compensation for the Fiscal Year		75,087		130,931		185,588		(376,158)
Compensation Actually Paid	$	5,305,593	$	2,096,450	$	2,087,247	$	2,452,588

Former PEO (Walsh) Summary Compensation Table Total to CAP Reconciliation
Fiscal Year	2021		2022		2023	2024
Summary Compensation Table Total	$	6,853,838		n/a	n/a	n/a
Deduct Change in Actuarial Present Value of Pension Plans Reported in Fiscal Year		—		—	—	—
Add Service Cost of Pension in Fiscal Year		571,123		—	—	—
Add Prior Service Cost of Pension in Fiscal Year		—		—	—	—
Deduct Grant Date Fair Value of Stock Awards Granted in Fiscal Year		(4,000,639)		—	—	—
Add-Deduct Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Awards Granted in Fiscal Year		5,650,907		—	—	—
Add-Deduct Change in Fair Value of Outstanding and Unvested Stock Awards Granted in Prior Fiscal Years		1,934,202		—	—	—
Add-Deduct Fair Value at Vesting of Stock Awards Granted in Fiscal Year That Vested During Fiscal Year		—		—	—	—
Add-Deduct Change in Fair Value as of Vesting Date of Stock Awards Granted in Prior Fiscal Years For Which Applicable Vesting Conditions Were Satisfied During Fiscal Year		175,908		—	—	—
Deduct Fair Value as of Prior Fiscal Year-End of Stock Awards Granted in Prior Fiscal Years That Failed to Meet Applicable Vesting Conditions During Fiscal Year		(18,130)		—	—	—
Add Dividends or Other Earnings Paid on Stock Awards in the Fiscal Year Prior to the Vesting Date that are not otherwise included in the Total Compensation for the Fiscal Year		170,940		—	—	—
Compensation Actually Paid	$	11,338,149		n/a	n/a	n/a

Non-PEO NEO Average Total Compensation Amount

$ 3,026,732

$ 2,146,817

$ 2,036,182

$ 2,326,699

Non-PEO NEO Average Compensation Actually Paid Amount

$ 2,505,455

508,745

526,688

3,345,437

Adjustment to Non-PEO NEO Compensation Footnote

The following amounts were deducted from/added to Summary Compensation Table total compensation in accordance with the SEC-mandated adjustments to calculate Compensation Actually Paid (“CAP”) to our PEO and average CAP to our non-PEO named executive officers. The fair value of equity awards was determined using methodologies and assumptions developed in a manner substantively consistent with those used to determine the grant date fair value of such awards.

Average other NEOs Summary Compensation Table Total to CAP Reconciliation
Fiscal Year	2021		2022		2023		2024
Average Summary Compensation Table Total	$	2,326,699	$	2,036,182	$	2,146,817	$	3,026,732
Deduct Change in Actuarial Present Value of Pension Plans Reported in Fiscal Year		(4,416)		—		(112,777)		(324,287)
Add Service Cost of Pension in Fiscal Year		40,323		48,571		24,384		26,187
Add Prior Service Cost of Pension in Fiscal Year		—		—		—		—
Deduct Grant Date Fair Value of Stock Awards Granted in Fiscal Year		(946,162)		(996,247)		(1,220,089)		(1,098,440)
Add-Deduct Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Awards Granted in Fiscal Year		1,336,445		479,065		170,192		833,860
Add-Deduct Change in Fair Value of Outstanding and Unvested Stock Awards Granted in Prior Fiscal Years		458,419		(1,148,318)		(294,986)		65,638
Add-Deduct Fair Value at Vesting of Stock Awards Granted in Fiscal Year That Vested During Fiscal Year		—		—		3,411		—
Add-Deduct Change in Fair Value as of Vesting Date of Stock Awards Granted in Prior Fiscal Years For Which Applicable Vesting Conditions Were Satisfied During Fiscal Year		93,323		76,365		48,985		8,316
Deduct Fair Value as of Prior Fiscal Year-End of Stock Awards Granted in Prior Fiscal Years That Failed to Meet Applicable Vesting Conditions During Fiscal Year		(2,135)		(12,696)		(254,651)		(60,141)
Add Dividends or Other Earnings Paid on Stock Awards in the Fiscal Year Prior to the Vesting Date that are not otherwise included in the Total Compensation for the Fiscal Year		42,941		43,766		(2,541)		27,590
Average Compensation Actually Paid for NEOs	$	3,345,437	$	526,688	$	508,745	$	2,505,455

Compensation Actually Paid vs. Total Shareholder Return

RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& TSR ​  ​ ​ RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& NET INCOME ​ ​  ​

Compensation Actually Paid vs. Net Income

RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& TSR ​  ​ ​ RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& NET INCOME ​ ​  ​

Compensation Actually Paid vs. Company Selected Measure

RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& ADJUSTED EPS ​  ​ ​
TABULAR LIST OF MOST IMPORTANT
PERFORMANCE MEASURES ​ ​ ● Adjusted EPS ● Safety - OSHA recordables ● OpEx reduction ● Excess Free Cash Flow ● Relative TSR

Total Shareholder Return Vs Peer Group

The following graphs present the relationship during 2024, 2023, 2022, and 2021 between (1) CAP to (a) each person serving as PEO and (b) our other NEOs on an average basis, and each of (2) (a) the Company’s and Peer Group’s TSR for such years and (b) the Company’s Net Income and Adjusted EPS for such years.

RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& TSR ​  ​ ​ RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& NET INCOME ​ ​  ​

Tabular List, Table

RELATIONSHIP BETWEEN
COMPENSATION ACTUALLY PAID
& ADJUSTED EPS ​  ​ ​
TABULAR LIST OF MOST IMPORTANT
PERFORMANCE MEASURES ​ ​ ● Adjusted EPS ● Safety - OSHA recordables ● OpEx reduction ● Excess Free Cash Flow ● Relative TSR

Total Shareholder Return Amount

$ 90.96

78.44

105.02

133.5

Peer Group Total Shareholder Return Amount

154.55

108.98

117.2

111.01

Net Income (Loss)

$ 461,000,000

$ (1,502,000,000)

$ 1,073,000,000

$ 1,467,000,000

Company Selected Measure Amount | $ / shares

3.06

2.84

2.9

2.96

PEO Name

Mr. Perreault

Mr. Perreault

Mr. Longhi

Mr. Walsh

Mr. Perreault

Mr. Perreault

Measure:: 1

Pay vs Performance Disclosure

Name

Adjusted EPS

Non-GAAP Measure Description

(4) Adjusted EPS is a Non-GAAP financial measure. For a discussion of adjustments, please see the “Executive Summary” section of our Compensation Discussion and Analysis (CD&A).

Measure:: 2

Pay vs Performance Disclosure

Name

Safety - OSHA recordables

Measure:: 3

Pay vs Performance Disclosure

Name

OpEx reduction

Measure:: 4

Pay vs Performance Disclosure

Name

Excess Free Cash Flow

Measure:: 5

Pay vs Performance Disclosure

Name

Relative TSR

Mr. Longhi

Pay vs Performance Disclosure

PEO Total Compensation Amount

$ 6,227,806

PEO Actually Paid Compensation Amount

6,190,474

Mr. Perreault

Pay vs Performance Disclosure

PEO Total Compensation Amount

5,346,550

$ 9,960,170

$ 6,060,694

$ 4,107,789

PEO Actually Paid Compensation Amount

2,452,588

2,087,247

2,096,450

5,305,593

Mr. Walsh

Pay vs Performance Disclosure

PEO Total Compensation Amount

6,853,838

PEO Actually Paid Compensation Amount

11,338,149

PEO | Mr. Longhi | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(3,039,803)

PEO | Mr. Longhi | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

2,830,513

PEO | Mr. Longhi | Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

171,958

PEO | Mr. Perreault | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(7,733,691)

(4,158,984)

(2,522,588)

PEO | Mr. Perreault | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

1,454,565

1,999,801

2,855,539

PEO | Mr. Perreault | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(1,912,144)

(2,073,984)

745,506

PEO | Mr. Perreault | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

168,939

151,830

48,425

PEO | Mr. Perreault | Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(2,517,804)

(36,180)

(13,838)

(4,165)

PEO | Mr. Perreault | Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(376,158)

185,588

130,931

75,087

PEO | Mr. Walsh | Pension Adjustments Service Cost

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

571,123

PEO | Mr. Walsh | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(4,000,639)

PEO | Mr. Walsh | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

5,650,907

PEO | Mr. Walsh | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

1,934,202

PEO | Mr. Walsh | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

175,908

PEO | Mr. Walsh | Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(18,130)

PEO | Mr. Walsh | Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

170,940

Non-PEO NEO | Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(324,287)

(112,777)

(4,416)

Non-PEO NEO | Pension Adjustments Service Cost

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

26,187

24,384

48,571

40,323

Non-PEO NEO | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(1,098,440)

(1,220,089)

(996,247)

(946,162)

Non-PEO NEO | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

833,860

170,192

479,065

1,336,445

Non-PEO NEO | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

65,638

(294,986)

(1,148,318)

458,419

Non-PEO NEO | Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

3,411

Non-PEO NEO | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

8,316

48,985

76,365

93,323

Non-PEO NEO | Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

(60,141)

(254,651)

(12,696)

(2,135)

Non-PEO NEO | Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year

Pay vs Performance Disclosure

Adjustment to Compensation, Amount

$ 27,590

$ (2,541)

$ 43,766

$ 42,941