Investment Securities (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Available-for-sale [Abstract]
Amortized cost	$ 567,939,000		$ 437,421,000
Gross unrealized gains	15,360,000		11,442,000
Gross unrealized losses	(1,080,000)		(659,000)
Total	582,219,000		448,204,000
Held-to-maturity [Abstract]
Amortized cost	17,796,000		18,044,000
Gross unrealized gains	143,000		138,000
Gross unrealized losses	(4,364,000)		(4,356,000)
Fair value	13,575,000		13,826,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	42		30
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	175,166,000		76,388,000
12 months or longer, Fair Value	2,496,000		2,549,000
Total, Fair Value	177,662,000		78,937,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(748,000)		(353,000)
12 months or longer, Unrealized losses	(332,000)		(306,000)
Total, Unrealized losses	(1,080,000)		(659,000)
Held-to-maturity, continuous unrealized loss position [Abstract]
Number of securities	4		4
Held-to-maturity, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	0		0
12 months or longer, Fair Value	9,179,000		9,423,000
Total, Fair Value	9,179,000		9,423,000
Held-to-maturity, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	0		0
12 months or longer, Unrealized losses	(4,364,000)		(4,356,000)
Total, Unrealized losses	(4,364,000)		(4,356,000)
Investment in Federal Home Loan and Atlantic Central Bankers Bank stock recorded at cost	4,596,000		5,088,000
Available-for-sale, Amortized cost [Abstract]
Due before one year	72,082,000
Due after one year through five years	170,391,000
Due after five years through ten years	25,249,000
Due after ten years	297,217,000
Other equity securities	3,000,000
Total	567,939,000
Available-for-sale, Fair value [Abstract]
Due before one year	72,292,000
Due after one year through five years	174,382,000
Due after five years through ten years	26,162,000
Due after ten years	306,373,000
Other equity securities	3,010,000
Total	582,219,000		448,204,000
Held-to-maturity, Amortized cost [Abstract]
Due before one year	0
Due after one year through five years	0
Due after five years through ten years	3,248,000
Due after ten years	14,548,000
Other equity securities	0
Total	17,796,000
Held-to-maturity, Fair value [Abstract]
Due before one year	0
Due after one year through five years	0
Due after five years through ten years	2,853,000
Due after ten years	10,722,000
Other equity securities	0
Total	13,575,000
Investment securities pledged to secure securities sold under repurchase agreements	39,500,000		44,600,000
Other than temporary impairment charges on one trust preferred pool security	126,000	75,000
Number of single issuer trust preferred securities	4
Number of pooled issuer trust preferred securities	2
Number of single issuer trust preferred securities issued by banks	2
Amortized cost of single issuer trust preferred securities issued by banks	4,300,000
Number of single issuer trust preferred securities issued by insurance companies	2
Amortized cost of single issuer trust preferred securities issued by insurance companies	12,000,000
U.S. Government agency securities [Member]
Available-for-sale [Abstract]
Amortized cost	8,804,000		9,087,000
Gross unrealized gains	242,000		198,000
Gross unrealized losses	0		0
Total	9,046,000		9,285,000
Available-for-sale, Fair value [Abstract]
Total	9,046,000		9,285,000
Federally insured student loan securities [Member]
Available-for-sale [Abstract]
Amortized cost	50,299,000
Gross unrealized gains	56,000
Gross unrealized losses	(79,000)
Total	50,276,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	6
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	43,440,000
12 months or longer, Fair Value	0
Total, Fair Value	43,440,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(79,000)
12 months or longer, Unrealized losses	0
Total, Unrealized losses	(79,000)
Available-for-sale, Fair value [Abstract]
Total	50,276,000
Tax-exempt obligations of states and political subdivisions
Available-for-sale [Abstract]
Amortized cost	107,957,000		94,227,000
Gross unrealized gains	4,530,000		3,580,000
Gross unrealized losses	(19,000)		(8,000)
Total	112,468,000		97,799,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	4		7
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	4,180,000		11,104,000
12 months or longer, Fair Value	0		0
Total, Fair Value	4,180,000		11,104,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(19,000)		(8,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(19,000)		(8,000)
Available-for-sale, Fair value [Abstract]
Total	112,468,000		97,799,000
Taxable obligations of states and political subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	44,519,000		50,778,000
Gross unrealized gains	3,042,000		2,149,000
Gross unrealized losses	(57,000)		(60,000)
Total	47,504,000		52,867,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	9		10
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	12,387,000		16,905,000
12 months or longer, Fair Value	0		0
Total, Fair Value	12,387,000		16,905,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(57,000)		(60,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(57,000)		(60,000)
Available-for-sale, Fair value [Abstract]
Total	47,504,000		52,867,000
Residential mortgage-backed securities [Member]
Available-for-sale [Abstract]
Amortized cost	195,236,000		190,214,000
Gross unrealized gains	3,401,000		3,582,000
Gross unrealized losses	(219,000)		(111,000)
Total	198,418,000		193,685,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	9		5
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	42,155,000		10,054,000
12 months or longer, Fair Value	0		0
Total, Fair Value	42,155,000		10,054,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(219,000)		(111,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(219,000)		(111,000)
Available-for-sale, Fair value [Abstract]
Total	198,418,000		193,685,000
Commercial mortgage-backed securities [Member]
Available-for-sale [Abstract]
Amortized cost	107,563,000		51,242,000
Gross unrealized gains	3,057,000		875,000
Gross unrealized losses	(308,000)		(56,000)
Total	110,312,000		52,061,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	7		4
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	50,734,000		24,421,000
12 months or longer, Fair Value	0		0
Total, Fair Value	50,734,000		24,421,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(308,000)		(56,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(308,000)		(56,000)
Available-for-sale, Fair value [Abstract]
Total	110,312,000		52,061,000
Other debt securities [Member]
Available-for-sale [Abstract]
Amortized cost	50,561,000		38,873,000
Gross unrealized gains	1,022,000		1,058,000
Gross unrealized losses	(398,000)		(399,000)
Total	51,185,000		39,532,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	7		3
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	22,270,000		10,929,000
12 months or longer, Fair Value	2,496,000		2,549,000
Total, Fair Value	24,766,000		13,478,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(66,000)		(93,000)
12 months or longer, Unrealized losses	(332,000)		(306,000)
Total, Unrealized losses	(398,000)		(399,000)
Available-for-sale, Fair value [Abstract]
Total	51,185,000		39,532,000
Other equity securities [Member]
Available-for-sale [Abstract]
Amortized cost	3,000,000		3,000,000
Gross unrealized gains	10,000		0
Gross unrealized losses	0		(25,000)
Total	3,010,000		2,975,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities			1
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value			2,975,000
12 months or longer, Fair Value			0
Total, Fair Value			2,975,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses			(25,000)
12 months or longer, Unrealized losses			0
Total, Unrealized losses			(25,000)
Available-for-sale, Fair value [Abstract]
Total	3,010,000		2,975,000
Other debt securities - single issuers [Member]
Held-to-maturity [Abstract]
Amortized cost	16,335,000		16,337,000
Gross unrealized gains	143,000		138,000
Gross unrealized losses	(4,113,000)		(4,051,000)
Fair value	12,365,000		12,424,000
Held-to-maturity, continuous unrealized loss position [Abstract]
Number of securities	2		2
Held-to-maturity, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	0		0
12 months or longer, Fair Value	7,969,000		8,021,000
Total, Fair Value	7,969,000		8,021,000
Held-to-maturity, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	0		0
12 months or longer, Unrealized losses	(4,113,000)		(4,051,000)
Total, Unrealized losses	(4,113,000)		(4,051,000)
Other debt securities - pooled [Member]
Held-to-maturity [Abstract]
Amortized cost	1,461,000		1,707,000
Gross unrealized gains	0		0
Gross unrealized losses	(251,000)		(305,000)
Fair value	1,210,000		1,402,000
Held-to-maturity, continuous unrealized loss position [Abstract]
Number of securities	2		2
Held-to-maturity, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	0		0
12 months or longer, Fair Value	1,210,000		1,402,000
Total, Fair Value	1,210,000		1,402,000
Held-to-maturity, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	0		0
12 months or longer, Unrealized losses	(251,000)		(305,000)
Total, Unrealized losses	$ (251,000)		$ (305,000)