Employee Benefit 401(k) Plans (Narrative) (Details) - USD ($)
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12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |
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| Minimum employee subscription rate, percentage of compensation |
1.00%
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| Maximum employee subscription rate, percentage of compensation |
60.00%
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| Employee pre-tax contributions vested percentage |
100.00%
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| Vesting rate |
20.00%
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| Percentage vested after total service period |
100.00%
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| Employees' vesting rights |
Participants are always 100 percent vested in their pre-tax contributions and will begin vesting in any matching or profit sharing contributions made on their behalf after two years of service with the Company at a rate of 20 percent per year, becoming 100 percent vested after a total of six years of service with the Company.
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| Expenses for employee benefit plan |
$ 886,000
|
$ 1,055,000
|
$ 1,029,000
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| Minimum [Member] |
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| Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |
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| Employer contribution vesting period |
2 years
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| Maximum [Member] |
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| Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] |
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| Employer contribution vesting period |
6 years
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