Pension Plan and Retirement Benefits - Defined Benefit Plans - Status (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Pension Plans
Change in Benefit Obligation:
Projected benefit obligation at beginning of year	$ 311,943	$ 288,559
Service cost	4,080	3,898	$ 3,971
Interest cost	12,050	11,203	11,989
Actuarial losses (gains)	32,370	21,861
Benefits paid	(23,105)	(13,578)
Projected benefit obligation at end of year	337,338	311,943	288,559
Change in Plan Assets:
Fair value of plan assets at beginning of year	205,498	216,962
Actual return on assets	18,792	(295)
Contribution to plan	6,778	2,409
Benefits paid	(23,105)	(13,578)
Fair value of plan assets at end of year	207,963	205,498	216,962
Funded Status of Plan:
Unfunded status	(129,375)	(106,445)
Postretirement Health Care Benefits
Change in Benefit Obligation:
Projected benefit obligation at beginning of year	110,534	105,387
Service cost	232	337	267
Interest cost	4,595	4,385	4,578
Actuarial losses (gains)	15,283	5,097
Benefits paid	(5,527)	(4,672)
Projected benefit obligation at end of year	125,117	110,534	$ 105,387
Change in Plan Assets:
Contribution to plan	5,527	4,672
Benefits paid	(5,527)	(4,672)
Funded Status of Plan:
Unfunded status	$ (125,117)	$ (110,534)

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of contributions made by the employer to defined benefit plans.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

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The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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