Investment Securities (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Available-for-sale [Abstract]
Amortized cost	$ 617,736,000		$ 437,421,000
Gross unrealized gains	18,073,000		11,442,000
Gross unrealized losses	(915,000)		(659,000)
Total	634,894,000		448,204,000
Held-to-maturity [Abstract]
Amortized cost	22,707,000		18,044,000
Gross unrealized gains	344,000		138,000
Gross unrealized losses	(4,417,000)		(4,356,000)
Fair value	18,634,000		13,826,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	32		30
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	108,954,000		76,388,000
12 months or longer, Fair Value	15,404,000		2,549,000
Total, Fair Value	124,358,000		78,937,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(598,000)		(353,000)
12 months or longer, Unrealized losses	(317,000)		(306,000)
Total, Unrealized losses	(915,000)		(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	9,042,000		9,423,000
Total, Fair Value	9,042,000		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	(4,417,000)		(4,356,000)
Total, Unrealized losses	(4,417,000)		(4,356,000)
Investment in Federal Home Loan and Atlantic Central Bankers Bank stock recorded at cost	4,200,000		5,100,000
Available-for-sale, Amortized cost [Abstract]
Due before one year	73,508,000
Due after one year through five years	158,815,000
Due after five years through ten years	36,614,000
Due after ten years	345,799,000
Other equity securities	3,000,000
Total	617,736,000
Available-for-sale, Fair value [Abstract]
Due before one year	73,622,000
Due after one year through five years	164,380,000
Due after five years through ten years	37,780,000
Due after ten years	356,037,000
Other equity securities	3,075,000
Total	634,894,000		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	8,240,000
Due after ten years	14,467,000
Other equity securities	0
Total	22,707,000
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	8,056,000
Due after ten years	10,578,000
Other equity securities	0
Total	18,634,000
Investment securities pledged to secure securities sold under repurchase agreements	37,000,000		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 single issuer trust preferred securities issued by banks	2
Amortized cost of single issuer trust preferred securities	16,300,000
Amortized cost of single issuer trust preferred securities issued by banks	4,200,000
Number of single issuer trust preferred securities issued by insurance companies	2
Amortized cost of single issuer trust preferred securities issued by insurance companies	12,100,000
Number of pooled issuer trust preferred securities	2
Amortized cost of pooled trust preferred securities	1,400,000
U.S. Government agency securities [Member]
Available-for-sale [Abstract]
Amortized cost	8,537,000		9,087,000
Gross unrealized gains	291,000		198,000
Gross unrealized losses	0		0
Total	8,828,000		9,285,000
Available-for-sale, Fair value [Abstract]
Total	8,828,000		9,285,000
Federally insured student loan securities [Member]
Available-for-sale [Abstract]
Amortized cost	111,197,000
Gross unrealized gains	483,000
Gross unrealized losses	(135,000)
Total	111,545,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	7
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	38,952,000
12 months or longer, Fair Value	0
Total, Fair Value	38,952,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(135,000)
12 months or longer, Unrealized losses	0
Total, Unrealized losses	(135,000)
Available-for-sale, Fair value [Abstract]
Total	111,545,000
Tax-exempt obligations of states and political subdivisions
Available-for-sale [Abstract]
Amortized cost	111,456,000		94,227,000
Gross unrealized gains	5,585,000		3,580,000
Gross unrealized losses	(1,000)		(8,000)
Total	117,040,000		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	3,479,000		11,104,000
12 months or longer, Fair Value	1,241,000		0
Total, Fair Value	4,720,000		11,104,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(1,000)		(8,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(1,000)		(8,000)
Available-for-sale, Fair value [Abstract]
Total	117,040,000		97,799,000
Taxable obligations of states and political subdivisions [Member]
Available-for-sale [Abstract]
Amortized cost	43,120,000		50,778,000
Gross unrealized gains	3,245,000		2,149,000
Gross unrealized losses	(30,000)		(60,000)
Total	46,335,000		52,867,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	7		10
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	7,715,000		16,905,000
12 months or longer, Fair Value	4,035,000		0
Total, Fair Value	11,750,000		16,905,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(20,000)		(60,000)
12 months or longer, Unrealized losses	(10,000)		0
Total, Unrealized losses	(30,000)		(60,000)
Available-for-sale, Fair value [Abstract]
Total	46,335,000		52,867,000
Residential mortgage-backed securities [Member]
Available-for-sale [Abstract]
Amortized cost	194,322,000		190,214,000
Gross unrealized gains	3,228,000		3,582,000
Gross unrealized losses	(392,000)		(111,000)
Total	197,158,000		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	43,529,000		10,054,000
12 months or longer, Fair Value	358,000		0
Total, Fair Value	43,887,000		10,054,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(386,000)		(111,000)
12 months or longer, Unrealized losses	(6,000)		0
Total, Unrealized losses	(392,000)		(111,000)
Available-for-sale, Fair value [Abstract]
Total	197,158,000		193,685,000
Commercial mortgage-backed securities [Member]
Available-for-sale [Abstract]
Amortized cost	98,417,000		51,242,000
Gross unrealized gains	4,116,000		875,000
Gross unrealized losses	(56,000)		(56,000)
Total	102,477,000		52,061,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	2		4
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	15,279,000		24,421,000
12 months or longer, Fair Value	0		0
Total, Fair Value	15,279,000		24,421,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	(56,000)		(56,000)
12 months or longer, Unrealized losses	0		0
Total, Unrealized losses	(56,000)		(56,000)
Available-for-sale, Fair value [Abstract]
Total	102,477,000		52,061,000
Other debt securities [Member]
Available-for-sale [Abstract]
Amortized cost	47,687,000		38,873,000
Gross unrealized gains	1,050,000		1,058,000
Gross unrealized losses	(301,000)		(399,000)
Total	48,436,000		39,532,000
Available-for-sale, continuous unrealized loss position [Abstract]
Number of securities	3		3
Available-for-sale, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months, Fair Value	0		10,929,000
12 months or longer, Fair Value	9,770,000		2,549,000
Total, Fair Value	9,770,000		13,478,000
Available-for-sale, continuous unrealized loss position, Unrealized losses [Abstract]
Less than 12 months, Unrealized losses	0		(93,000)
12 months or longer, Unrealized losses	(301,000)		(306,000)
Total, Unrealized losses	(301,000)		(399,000)
Available-for-sale, Fair value [Abstract]
Total	48,436,000		39,532,000
Other equity securities [Member]
Available-for-sale [Abstract]
Amortized cost	3,000,000		3,000,000
Gross unrealized gains	75,000		0
Gross unrealized losses	0		(25,000)
Total	3,075,000		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	3,075,000		2,975,000
Other debt securities - single issuers [Member]
Held-to-maturity [Abstract]
Amortized cost	21,335,000		16,337,000
Gross unrealized gains	344,000		138,000
Gross unrealized losses	(4,181,000)		(4,051,000)
Fair value	17,498,000		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	7,906,000		8,021,000
Total, Fair Value	7,906,000		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	(4,181,000)		(4,051,000)
Total, Unrealized losses	(4,181,000)		(4,051,000)
Other debt securities - pooled [Member]
Held-to-maturity [Abstract]
Amortized cost	1,372,000		1,707,000
Gross unrealized gains	0		0
Gross unrealized losses	(236,000)		(305,000)
Fair value	1,136,000		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	1,136,000		1,402,000
Total, Fair Value	1,136,000		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	(236,000)		(305,000)
Total, Unrealized losses	$ (236,000)		$ (305,000)