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Income Taxes (Details Textual) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Income Tax Disclosure [Abstract] |  |  |
Deferred Tax Assets, Valuation Allowance | $ 0 us-gaap_DeferredTaxAssetsValuationAllowance |  |
Income Taxes (Textual) [Abstract] |  |  |
Income tax benefit to shareholders equity | 1,000,000 us-gaap_IncomeTaxEffectsAllocatedDirectlyToEquity | 800,000 us-gaap_IncomeTaxEffectsAllocatedDirectlyToEquity | 2,000,000 us-gaap_IncomeTaxEffectsAllocatedDirectlyToEquity
Tax benefit not previously claimed by the company | $ 296,755 dhil_TaxBenefitFromDividendPaymentsRelatedToRestrictedStockGrants | $ 357,188 dhil_TaxBenefitFromDividendPaymentsRelatedToRestrictedStockGrants | $ 1,992,298 dhil_TaxBenefitFromDividendPaymentsRelatedToRestrictedStockGrants

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- Definition Tax benefit from dividend payments related to restricted stock grants. + References No definition available. + Details
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319 + Details
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- Definition The sum of the tax effects of all items occurring during the period that have been charged or credited directly to other comprehensive income or to related components of shareholders' equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32672-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=18498875&loc=d3e39076-109324 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d),(e) -URI http://asc.fasb.org/extlink&oid=18498875&loc=d3e38679-109324 + Details
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