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Significant Accounting Policies - Mutual Fund Administration Gross and Net Revenue (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Mutual fund administration:
Administration revenue, gross	$ 6,379,960us-gaap_AdministrativeServicesRevenue	$ 5,043,417us-gaap_AdministrativeServicesRevenue
12b-1/service fees and commission revenue received from fund clients	2,744,151us-gaap_FeesAndCommissions	2,481,771us-gaap_FeesAndCommissions
12b-1/service fees and commission expense payments to third parties	(2,373,863)dhil_ServiceFeesAndCommissionExpensePaymentsToThirdParties	(2,156,513)dhil_ServiceFeesAndCommissionExpensePaymentsToThirdParties
Fund related expense	(2,838,794)dhil_FundRelatedExpense	(2,089,175)dhil_FundRelatedExpense
Revenue, net of related expenses	3,911,454dhil_RevenueFromAdministrativeServicesExcludingFinancialActivityNet	3,279,500dhil_RevenueFromAdministrativeServicesExcludingFinancialActivityNet
DHCM C-Share financing:
Broker commission advance repayments	251,360dhil_BrokerCommissionAdvanceRepayments	173,890dhil_BrokerCommissionAdvanceRepayments
Broker commission amortization	(244,943)dhil_BrokerCommissionAmortization	(175,100)dhil_BrokerCommissionAmortization
Financing activity, net	6,417dhil_FinancingActivityNet	(1,210)dhil_FinancingActivityNet
Mutual fund administration revenue, net	$ 3,917,871dhil_RevenueFromAdministrativeServicesNet	$ 3,278,290dhil_RevenueFromAdministrativeServicesNet

X

- Definition

Broker commission advance repayments.

+ References

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- Definition

Broker commission amortization.

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- Definition

Financing activity, net.

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- Definition

Fund related expense.

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- Definition

Revenue from administrative services excluding financial activity net.

+ References

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- Definition

Revenue from administrative services net.

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- Definition

Service fees and commission expense payments to third parties.

+ References

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- Definition

Amount of revenue from providing administrative services, including, but not limited to, accounting, tax, legal, regulatory filing, and share registration activities of managed funds and investment accounts of independent third parties and related and affiliated entities.

+ References

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- Definition

Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 9

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