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Employee Benefit Plan (Details) | 12 Months Ended
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Dec. 31, 2017 USD ($) Officers | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Profit Sharing and 401(k) Plan for eligible employees [Member] |  |  |
Employee Benefit Plan (Textual) |  |  |
Defined benefit plan, annual cost | $ 476,000 | $ 356,000 | $ 326,000
Supplemental Executive Retirement Plan (nonqualified deferred compensation plan) [Member] |  |  |
Employee Benefit Plan (Textual) |  |  |
Defined benefit plan, annual cost | $ 792,000 | 782,000 | $ 978,000
Number of executive officers | Officers | 20 |  |
Accrued benefit obligation | $ 5,400,000 | $ 4,600,000 |

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- Definition Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15(a)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15(5)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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