Post Retirement Benefits - Change in Benefit Obligation (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in benefit obligation:
Interest cost	$ 277,000us-gaap_DefinedBenefitPlanInterestCost	$ 332,000us-gaap_DefinedBenefitPlanInterestCost	$ 364,000us-gaap_DefinedBenefitPlanInterestCost
Postretirement benefits
Change in benefit obligation:
Benefit obligation at beginning of year	6,774,000	9,987,000
Interest cost	277,000	332,000
Unrecognized (gain) loss	2,726,000	(2,917,000)
Benefits paid	(605,000)	(628,000)
Benefit obligation at beginning of year	9,172,000	6,774,000
Plan Assets	0	0
Amounts recorded in accumulated other comprehensive income:
Prior service credit	(8,090,000)	(8,586,000)
Net loss	4,156,000	1,477,000
Total	$ (3,934,000)	$ (7,109,000)
Weighted-average assumptions:
Discount rate used to determine benefit obligation and net periodic benefit cost	3.80%	4.60%

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost, Discount Rate

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- Definition

The pretax total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.

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The pretax net amount of gains and losses that are not yet recognized as a component of net periodic benefit cost, and that are recognized as increases or decreases in other comprehensive income as they arise. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.

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- Definition

Amount related to the pretax cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost.

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- Definition

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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- Definition

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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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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- Definition

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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