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Retirement Plans (Changes in Fair Value of Securities Using Significant Unobservable Inputs) (Details) (Retirement Income Plan [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair value of assets, beginning of year	$ 182,614,000	$ 173,311,000
Total gains (realized and unrealized) included in changes in net assets	21,896,000	6,526,000
Fair value of assets, end of year	207,150,000	182,614,000
Significant Unobservable Inputs (Level 3) [Member] | Alternative Investments [Member]
Fair value of assets, beginning of year	15,180,000	17,179,000
Total gains (realized and unrealized) included in changes in net assets	1,118,000	1,949,000
Purchases	434,000	1,176,000
Sales	0	0
Issuances	0	0
Settlements	(4,142,000)	(5,124,000)
Transfers into level 3	41,000	0
Transfers out of level 3	0	0
Fair value of assets, end of year	$ 12,631,000	$ 15,180,000

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- Definition

Issues that have taken place during the period in relation to plan assets.

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Transfers out of Level 3. For example, transfers due to changes in the observability of significant inputs.

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- Definition

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.

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The amount of increase in the plan assets attributed to a business combination.

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The amount of decrease in the plan assets attributed to the sale, liquidation, spin-off or other divestiture of a corporate division or subsidiary.

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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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The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts.

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