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BENEFIT PLANS, 401(K) Employee Stock Ownership Plan (Details) - 401(k) Employee Stock Ownership Plan [Member] - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Contribution Plan [Abstract] |  |  |
Percentage of first eligible compensation fully matched by employer | 3.00% |  |
Percentage of matching contribution in the form of common stock | 100.00% |  |
Percentage of the next eligible compensation matched at 50% by employer | 3.00% |  |
Percentage of matching contributions for the next eligible compensation in the form of company stock | 50.00% |  |
(Income)/expense recognized under plan | $ 6.1 | $ 5.9 | $ 5.3
Interest credit contribution expense recognized for 401(k) plan | $ 1.1 | $ 0.9 | $ 0.8
Minimum [Member] |  |  |
Defined Contribution Plan [Abstract] |  |  |
Contribution from eligible compensation | 1.00% |  |
Maximum [Member] |  |  |
Defined Contribution Plan [Abstract] |  |  |
Contribution from eligible compensation | 90.00% |  |

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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