Percentage investment in common stock of large-cap U.S. companies.

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- Definition

The percentage of insurance contracts in common stock of small-cap companies.

+ References

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- Definition

Percentage investment in corporate bonds.

+ References

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- Definition

Percentage investment in mortgage backed securities.

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No definition available.

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- Definition

Percentage investment in U.S. Government securities.

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- Definition

Percentage investment in other investments

+ References

No definition available.

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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.

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Fair value - other postretirement (Details 9) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Percentage investment in common stock of small-cap companies	10.00%	11.00%
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 82,516,000	$ 88,739,000	$ 82,846,000
Percentage investment in corporate bonds	51.00%	38.00%
Percentage investment in common stock of large-cap U.S. companies	23.00%	23.00%
Percentage Investment in US Government Securities	7.00%	21.00%
Percentage investment in common stock of small-cap companies	7.00%
Percentage investment in mortgage backed securities		9.00%
Percentage investment in other investments	12.00%	9.00%
Estimated future employer contributions in next fiscal year	$ 700,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	3,866,000	$ 4,815,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Equity securities of U.S. companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	1,767,000	2,316,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Equities securities of International companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	2,000	4,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	76,881,000	81,604,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	82,516,000	88,739,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Equity securities of U.S. companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	1,767,000	2,316,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Equities securities of International companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year		4,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	1,000	3,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	1,768,000	2,323,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Significant Other Observable Inputs (Level 2) \| Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	3,866,000	4,815,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Significant Other Observable Inputs (Level 2) \| Equities securities of International companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	2,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Significant Other Observable Inputs (Level 2) \| Insurance investment contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	76,880,000	81,601,000
Other Postretirement Benefits \| Qualified Plan [Member] \| Underfunded Plan [Member] \| Significant Other Observable Inputs (Level 2) \| Total assets measured at fair value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets at end of year	$ 80,748,000	$ 86,416,000