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401(k) and Employee Stock Ownership Plan (Details) - USD ($) | 12 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
Retirement Benefits [Abstract] |  |  |
Employee contribution, percentage of annual salary | 100.00% |  |
Employee contribution, maximum allowable contribution | $ 54,000 |  |
Service period for eligibility (in years) | 1 year |  |
Number of hours of service required in 12 months for plan eligibility (in hours) | 1000 hours |  |
Employer matching contribution percent | 100.00% |  |
Percent of employees' gross pay | 4.00% |  |
Term for employees to become fully vested (in years) | 6 years |  |
Profit sharing contribution, percent | 7.00% |  |
Company contributions to plan | $ 6,433,000 | $ 7,600,000 | $ 8,700,000

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -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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