Benefit Plans (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Benefit Obligation, Remaining Liability	$ 7,221	$ 6,777	$ 6,629
Benefits paid	(563)	(771)
Unvested stock amortization	143	80
Profit Sharing Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	The Bank maintains a Profit Sharing Plan for eligible employees. The plan provides that the Bank make contributions equal to 3% of the eligible participant's W-2 wages. DNB's related expense associated with the Profit Sharing Plan was $225,000 and $219,000 in 2012 and 2011, respectively.
Compensation expense	225	219
Pension Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	The Bank maintains a defined benefit pension plan (the "Plan") covering all employees, including officers, who have been employed for one year and have attained 21 years of age. Prior to May 1, 1985, an individual must have attained the age of 25 and accrued one year of service. The Plan provides pension benefits to eligible retired employees at 65 years of age equal to 1.5% of their average monthly pay multiplied by their years of accredited service (maximum 40 years). The accrued benefit is based on the monthly average of their highest five consecutive years of their last ten years of service. The Plan generally covers only full-time employees.
Defined Benefit Plan, Description of Plan Amendment	Effective December 31, 2003, DNB amended its Plan to curtail future eligibility and so that no participants will earn additional benefits under the Plan after December 31, 2003. As a result of this amendment, no further service or compensation was credited under the Plan after December 31, 2003. The Plan, although frozen, will continue to provide benefit payments and employees can still earn vesting credits until retirement.
The Replacement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	The Replacement Plan provides that the Bank and the Executive share in the rights to the cash surrender value and death benefits of a split-dollar life insurance policy (the "Policy") The policy is designed to provide the Executive, upon attaining age 65, with projected annual after-tax payments of approximately $35,000. In addition, the Policy is intended to provide the Executive with a projected death benefit of $750,000.
Benefit Obligation, Remaining Liability	729	730
Benefits paid	51	41
Supplemental Employee Retirement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	On December 20, 2006, the Board of Directors of DNB Financial Corporation approved, and effective April 1, 2007 and December 8, 2008 modified, a Supplemental Executive Retirement Plan (also known as a SERP) for its Chairman and Chief Executive Officer, William S. Latoff. The purpose of the SERP is to provide Mr. Latoff a pension supplement beginning at age 70 for 15 years in approximately equal amounts each year and to compensate him for the loss of retirement plan funding opportunities from his other business interests because of his commitments to DNB as Chairman and CEO.
Benefit Obligation, Remaining Liability	1,200	1,100
Benefits paid	63	67
401(k) Retirement Savings Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	In 1994, the Bank adopted a retirement savings plan intended to comply with Section 401(k) of the Internal Revenue Code of 1986. Participants are permitted to authorize pre-tax savings contributions to a separate trust established under the 401(k) plan, subject to limitations on deductibility of contributions imposed by the Internal Revenue Code. Effective July 1, 2007 the Bank amended the plan to allow after-tax contributions to be made as well. The contributions are subject to the same limitations. Effective January 1, 2010, management indicated that it would evaluate discretionary matching contributions each quarter based upon DNB's financial performance. DNB made no matching contributions to the 401(k) plan in 2012 and 2011.
Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
General Discussion of Pension and Other Postretirement Benefits	DNB has a Stock Option Plan for employees and directors. Under the plan, options (both qualified and non-qualified) to purchase a maximum of 793,368 (as adjusted for subsequent stock dividends) shares of DNB's common stock could be issued to employees and directors.
Maximum number of shares	793,368
Shares available for future grants	327,964	156,144
Award Vesting Period, Description	All options with the exception of 44,600 options granted on April 23, 2010 and 44,600 options granted on December 12, 2011 are immediately exercisable.
Unvested stock amortization	69	27
Stock Option Plan, Grant Date 4/23/2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares	100
Fair value per share	$ 2.25
Risk free interest rate	3.273%
Dividend yield	1.73%
Volatility	35.564%
Award Vesting Period, Description	subject to four year cliff vesting
Stock expiration date	Apr. 23, 2017
Exercise price per share	$ 6.93
Restrictions on resale of shares	2 years
Restrictions of exercising options, Description	These options are exercisable only at and after such time as the market value of the common stock first equals or exceeds $7.97, which is 115% of the $6.93 exercise price
Cost Not yet Recognized	31
Cost Not yet Recognized, Period for Recognition	1 year 3 months 23 days
Stock Option Plan, Grant Date 12/12/2011 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares	141
Fair value per share	$ 3.17
Risk free interest rate	1.445%
Dividend yield	1.16%
Volatility	36.513%
Award Vesting Period, Description	subject to three year cliff vesting
Stock expiration date	Dec. 12, 2018
Exercise price per share	$ 10.31
Restrictions on resale of shares	2 years
Restrictions of exercising options, Description	These options are exercisable only at and after such time as the market value of the common stock first equals or exceeds $11.34, which is 110% of the $10.31 exercise price
Cost Not yet Recognized	91
Cost Not yet Recognized, Period for Recognition	1 year 11 months 12 days
Incentive Equity And Deferred Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares	243,101
Shares available for future grants	158,354
Award Vesting Period, Description	three-year cliff-vesting period
Unvested stock amortization	74	61
Cost Not yet Recognized	$ 418
Cost Not yet Recognized, Period for Recognition	1 year 11 months 19 days