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Benefit Plans Components of Benefit Plans (Details) | 12 Months Ended
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Dec. 31, 2015 | Sep. 30, 2015 USD ($) Years Number_of_defined_benefit_plan_structures plans Number_of_defined_benefit_plan_investment_funds | Dec. 31, 2014 | Sep. 30, 2014 USD ($) | Sep. 30, 2013 USD ($)
Defined Benefit Plan Disclosure |  |  |  |  |
Number of defined benefit plans |  | 1 |  |  |
Number of defined contribution plans |  | 1 |  |  |
Number of unfunded post-retirement health care plans | plans |  | 2 |  |  |
Number of benefit plan structures | Number_of_defined_benefit_plan_structures |  | 2 |  |  |
Number of consecutive highest base pay years | Years |  | 3 |  |  |
Percentage of straight-time earnings for cash balance benefit credit |  | 6.00% |  |  |
Percentage added to consumer price index for interest credit of cash balance benefit |  | 3.00% |  |  |
Minimum interest credit percentage for cash balance benefit |  | 6.00% |  |  |
Maximum interest credit percentage for cash balance benefit |  | 10.00% |  |  |
Rate of cash balance benefit credit for calendar year |  |  | 6.00% |  |
Number of defined benefit plan investment funds | Number_of_defined_benefit_plan_investment_funds |  | 2 |  |  |
Fixed and variable fund annual maximum contribution |  | $ 10,000 |  |  |
Fixed fund balance interest credits after January 1, 2010 |  | 6.00% |  |  |
Fixed fund balance credit percentage subtracted from the actuarial rate of return after January 1, 2010 |  | 0.50% |  |  |
Fixed fund interest credit rate |  | 6.00% |  | 6.00% |
Fixed fund interest credit amount |  | $ 26,000,000 |  | $ 33,000,000 |
Defined contribution plan contribution amount |  | $ 36,000,000 |  | $ 35,000,000 | $ 34,000,000
Market-related value phase-in period number of years | Years |  | 3 |  |  |
Original benefit structure |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined contribution plan employer matching contribution rate |  | $ 0.25 |  |  |
Cash Balance Benefit Structure |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined contribution plan employer matching contribution rate |  | 0.75 |  |  |
Defined Contribution Only |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined contribution plan employer matching contribution rate |  | $ 0.75 |  |  |
Defined Contribution Plan, Automatic Employer Contribution |  | 4.50% |  |  |
Maximum | Original benefit structure |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  | 1.50% |  |  |
Maximum | Cash Balance Benefit Structure |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  | 4.50% |  |  |
Maximum | Defined Contribution Only |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  | 4.50% |  |  |
Scenario, Forecast [Member] |  |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |  |
Rate of cash balance benefit credit for calendar year | 6.00% |  |  |  |

X
- Definition Automatic, non-elective percentage of base compensation that employer contributes to participants account in the defined contribution plan only. + References No definition available. + Details
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- Definition The amount per dollar that an employer matches employee contributions to a defined contribution plan. + References No definition available. + Details
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- Definition The maximum annual contribution that employees can make to the fixed and variable fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on contributions made by employees. The variable fund is a benefit that invests employee contributions in the Spartan U.S. Equity Index Fund-Fidelity Advantage Class (Spartan). + References No definition available. + Details
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- Definition The interest rate subtracted from the actuarial return and compared to six percent to credit balances in the fixed fund benefit after January 1, 2010. The lesser of the two interest rates is used to credit the fixed fund balances. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions. + References No definition available. + Details
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- Definition The interest rate compared to the actuarial return less 0.5 percent to credit balances in a fixed fund benefit after January 1, 2010. The lesser of the two interest rates is used to credit the fixed fund balances. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions. + References No definition available. + Details
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- Definition The amount of interest credited to balances in the fixed fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions. + References No definition available. + Details
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- Definition The interest rate used to credit balances in the fixed fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions. + References No definition available. + Details
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- Definition The number of years for the phase-in period in which the impact of asset performance on pension expense is phased-in through a market-related value of asset calculation. + References No definition available. + Details
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- Definition The maximum interest credit percentage for accounts of members of the Cash Balance Benefit. + References No definition available. + Details
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- Definition The minimum interest credit percentage for accounts of memebers of the Cash Balance Benefit. + References No definition available. + Details
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- Definition The number of consecutive highest base pay years used to calculate the member's average monthly salary for those members participating in the Original Benefit Structure. + References No definition available. + Details
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- Definition The number of qualified defined benefit pension plans. + References No definition available. + Details
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- Definition The number of qualified defined contribution pension plans. + References No definition available. + Details
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- Definition The number of unfunded post-retirement health care plans that provide for non-vested contributions toward the cost of certain retirees' medical coverage. + References No definition available. + Details
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- Definition Number of defined benefit plan pension structures + References No definition available. + Details
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- Definition The number of defined benefit plan investment funds. + References No definition available. + Details
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- Definition The percentage added to the consumer price index for the interest credit to members' accounts of the Cash Balance Benefit + References No definition available. + Details
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- Definition The percentage of straight-time earnings that is used to credit the accounts of Cash Balance Benefit members. + References No definition available. + Details
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- Definition The percentage of Cash Balance Benefit credit for specific calendar years. + References No definition available. + Details
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- 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
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- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Details
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