Investment Securities (Details) (USD $)	6 Months Ended				12 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 488,919,000		$ 417,705,000		$ 471,767,000
Gross Unrealized Gains	12,990,000		7,278,000		8,205,000
Gross Unrealized Losses	17,000		1,068,000		152,000
Fair/Book Value	501,892,000		423,915,000		479,820,000
Less Than 12 Months [Abstract]
Fair Value	8,179,000		138,276,000		90,077,000
Unrealized Loss	68,000		1,075,000		152,000
12 Months or More [Abstract]
Fair Value	0		0		0
Unrealized Loss	0		0		0
Total [Abstract]
Fair Value	8,179,000		138,276,000		90,077,000
Unrealized Loss	68,000		1,075,000		152,000
Schedule of Held-to-maturity Securities [Line Items]
Book Value	70,195,000		63,584,000		63,092,000
Gross Unrealized Gains	2,523,000		2,036,000		2,782,000
Gross Unrealized Losses	51,000		7,000		0
Fair Value	72,667,000		65,613,000		65,874,000
Securities Available-for-Sale [Abstract]
Within 1 Year	13,085,000
After 1 but Within 5	54,244,000
After 5 but Within 10	130,254,000
Over 10 years	304,309,000
Total Fair Value	501,892,000		423,915,000		479,820,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Within 1 Year	1,025,000
After 1 but Within 5	10,739,000
After 5 but Within 10	42,873,000
Over 10 years	15,558,000
Book Value	70,195,000		63,584,000		63,092,000
Proceeds from calls of securities [Abstract]
Proceeds from calls of securities	26,530,000		55,000,000		201,135,000
Gains from calls of securities	0		0		94,000
Realized losses from call of securities	0		0		0
Number of investment securities held	329
Number of loss positions less than twelve months	27
Number of loss positions in twelve months or more	0
Percentage of bank qualified municipal bond portfolio rated (in hundredths)	93.00%
Percentage of portfolio not rated (in hundredths)	7.00%
Securities pledged to secure public deposits, FHLB borrowings, and other government agency deposits as required by law	314,900,000				373,200,000
Obligations of States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Book Value	67,159,000		59,648,000		59,640,000
Gross Unrealized Gains	2,498,000		1,964,000		2,736,000
Gross Unrealized Losses	51,000		7,000		0
Fair Value	69,606,000		61,605,000		62,376,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Book Value	67,159,000		59,648,000		59,640,000
Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Book Value	806,000	[1]	1,673,000	[1]	1,205,000	[1]
Gross Unrealized Gains	25,000	[1]	72,000	[1]	46,000	[1]
Gross Unrealized Losses	0	[1]	0	[1]	0	[1]
Fair Value	831,000	[1]	1,745,000	[1]	1,251,000	[1]
Held-to-maturity Securities, Debt Maturities [Abstract]
Book Value	806,000	[1]	1,673,000	[1]	1,205,000	[1]
Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Book Value	2,230,000		2,263,000		2,247,000
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	2,230,000		2,263,000		2,247,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Book Value	2,230,000		2,263,000		2,247,000
Government Agency & Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	56,764,000		217,724,000		82,195,000
Gross Unrealized Gains	314,000		496,000		413,000
Gross Unrealized Losses	0		384,000		13,000
Fair/Book Value	57,078,000		217,836,000		82,595,000
Less Than 12 Months [Abstract]
Fair Value			86,806,000		4,987,000
Unrealized Loss			384,000		13,000
12 Months or More [Abstract]
Fair Value			0		0
Unrealized Loss			0		0
Total [Abstract]
Fair Value			86,806,000		4,987,000
Unrealized Loss			384,000		13,000
Schedule of Held-to-maturity Securities [Line Items]
Book Value	67,159,000
Securities Available-for-Sale [Abstract]
Within 1 Year	10,031,000
After 1 but Within 5	45,845,000
After 5 but Within 10	1,202,000
Over 10 years	0
Total Fair Value	57,078,000		217,836,000		82,595,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Within 1 Year	1,025,000
After 1 but Within 5	9,928,000
After 5 but Within 10	40,648,000
Over 10 years	15,558,000
Book Value	67,159,000
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,724,000		5,620,000		5,782,000
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair/Book Value	5,724,000		5,620,000		5,782,000
Less Than 12 Months [Abstract]
Fair Value	4,774,000		1,494,000
Unrealized Loss	51,000		7,000
12 Months or More [Abstract]
Fair Value	0		0
Unrealized Loss	0		0
Total [Abstract]
Fair Value	4,774,000		1,494,000
Unrealized Loss	51,000		7,000
Securities Available-for-Sale [Abstract]
Within 1 Year	0
After 1 but Within 5	0
After 5 but Within 10	221,000
Over 10 years	5,503,000
Total Fair Value	5,724,000		5,620,000		5,782,000
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	414,990,000		194,051,000		383,380,000
Gross Unrealized Gains	12,647,000		6,782,000		7,792,000
Gross Unrealized Losses	0		684,000		139,000
Fair/Book Value	427,637,000		200,149,000		391,033,000
Less Than 12 Months [Abstract]
Fair Value			49,976,000		85,090,000
Unrealized Loss			684,000		139,000
12 Months or More [Abstract]
Fair Value			0		0
Unrealized Loss			0		0
Total [Abstract]
Fair Value			49,976,000		85,090,000
Unrealized Loss			684,000		139,000
Schedule of Held-to-maturity Securities [Line Items]
Book Value	806,000
Securities Available-for-Sale [Abstract]
Within 1 Year	0
After 1 but Within 5	0
After 5 but Within 10	128,831,000
Over 10 years	298,806,000
Total Fair Value	427,637,000		200,149,000		391,033,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Within 1 Year	0
After 1 but Within 5	806,000
After 5 but Within 10	0
Over 10 years	0
Book Value	806,000
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,983,000
Gross Unrealized Gains	29,000
Gross Unrealized Losses	17,000
Fair/Book Value	8,995,000
Less Than 12 Months [Abstract]
Fair Value	3,405,000
Unrealized Loss	17,000
12 Months or More [Abstract]
Fair Value	0
Unrealized Loss	0
Total [Abstract]
Fair Value	3,405,000
Unrealized Loss	17,000
Securities Available-for-Sale [Abstract]
Within 1 Year	596,000
After 1 but Within 5	8,399,000
After 5 but Within 10	0
Over 10 years	0
Total Fair Value	8,995,000
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,458,000		310,000		410,000
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair/Book Value	2,458,000		310,000		410,000
Schedule of Held-to-maturity Securities [Line Items]
Book Value	2,230,000
Securities Available-for-Sale [Abstract]
Within 1 Year	2,458,000
After 1 but Within 5	0
After 5 but Within 10	0
Over 10 years	0
Total Fair Value	2,458,000		310,000		410,000
Held-to-maturity Securities, Debt Maturities [Abstract]
Within 1 Year	0
After 1 but Within 5	5,000
After 5 but Within 10	2,225,000
Over 10 years	0
Book Value	$ 2,230,000

[1] All Mortgage Backed Securities consist of securities collateralized by residential real estate and were issued by an agency or government sponsored entity of the U.S. government. Fair values are based on quoted market prices or dealer quotes. If a quoted market price or dealer quote is not available, fair value is estimated using quoted market prices for similar securities.