Securities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,120,384,000	$ 1,213,934,000
Unrealized gains	27,794,000	30,839,000
Unrealized losses	179,000	154,000
Estimated fair value	1,147,999,000	1,244,619,000
Amortized cost of mortgage-backed securities comprised of Government Sponsored Enterprise Securities	221,100,000	290,200,000
Fair value of mortgage-backed securities comprised of Government Sponsored Enterprise Securities	232,300,000	303,000,000
Amortized cost of mortgage-backed securities comprised of US Government Agency Securities	16,400,000	20,500,000
Fair value of mortgage-backed securities comprised of US Government Agency Securities	18,000,000	22,400,000
Amortized cost of collateralized mortgage obligations comprised of Government Sponsored Enterprise Securities	399,200,000	398,300,000
Fair value of collateralized mortgage obligations comprised of Government Sponsored Enterprise Securities	403,600,000	402,400,000
Amortized cost of collateralized mortgage obligations comprised of US Government Agency Securities	44,800,000	60,800,000
Fair value of collateralized mortgage obligations comprised of US Government Agency Securities	46,200,000	63,100,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	40,397,000	63,966,000
12 Months or Longer, Fair Value	167,000	377,000
Total, Fair Value	40,564,000	64,343,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(97,000)	(153,000)
12 Months or Longer, Unrealized Losses	(82,000)	(1,000)
Total, Unrealized Losses	(179,000)	(154,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	7	11
12 Months or Longer, Number of Positions	1	2
Total, Number of Positions	8	13
Sales transactions of securities available for sale [Abstract]
Proceeds from sales	1,790,000	2,437,000	103,253,000
Gross realized gains	442,000	7,000	3,170,000
Gross realized losses	0	(165,000)	(25,000)
Net securities gains (losses)	442,000	(158,000)	3,145,000
Gains from calls on securities available for sale	200,000	300,000	100,000
Amortized costs of securities available for sale pledged to secure public deposits	1,200,000,000	1,200,000,000
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	209,000,000
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	60,563,000	70,811,000
Unrealized gains	972,000	1,387,000
Unrealized losses	0	0
Estimated fair value	61,535,000	72,198,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	26,678,000
From one to five years	193,142,000
From five to ten years	311,575,000
After ten years	577,779,000
Total, Amortized Cost	1,109,174,000
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	26,788,000
From one to five years	195,953,000
From five to ten years	319,229,000
After ten years	592,075,000
Total, Fair Value	1,134,045,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	25,184,000
From one to five years	27,413,000
From five to ten years	5,425,000
After ten years	2,541,000
Securities held to maturity	60,563,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	25,258,000
From one to five years	28,118,000
From five to ten years	5,434,000
After ten years	2,725,000
Total, Fair Value	61,535,000
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%	10.00%
Mortgage-backed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	1,168,000	1,447,000
Unrealized gains	184,000	213,000
Unrealized losses	0	0
Estimated fair value	1,352,000	1,660,000
State & Municipal [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	59,395,000	69,364,000
Unrealized gains	788,000	1,174,000
Unrealized losses	0	0
Estimated fair value	60,183,000	70,538,000
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	63,668,000	81,006,000
Unrealized gains	757,000	1,228,000
Unrealized losses	0	0
Estimated fair value	64,425,000	82,234,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	0	0
12 Months or Longer, Fair Value	0	0
Total, Fair Value	0	0
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Longer, Unrealized Losses	0	0
Total, Unrealized Losses	0	0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	0	0
12 Months or Longer, Number of Positions	0	0
Total, Number of Positions	0	0
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	281,398,000	254,983,000
Unrealized gains	1,507,000	879,000
Unrealized losses	91,000	16,000
Estimated fair value	282,814,000	255,846,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	39,906,000	34,996,000
12 Months or Longer, Fair Value	0	0
Total, Fair Value	39,906,000	34,996,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(91,000)	(16,000)
12 Months or Longer, Unrealized Losses	0	0
Total, Unrealized Losses	(91,000)	(16,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	4	3
12 Months or Longer, Number of Positions	0	0
Total, Number of Positions	4	3
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	82,675,000	99,176,000
Unrealized gains	4,127,000	5,624,000
Unrealized losses	0	11,000
Estimated fair value	86,802,000	104,789,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	0	957,000
12 Months or Longer, Fair Value	0	377,000
Total, Fair Value	0	1,334,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	0	(10,000)
12 Months or Longer, Unrealized Losses	0	(1,000)
Total, Unrealized Losses	0	(11,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	0	3
12 Months or Longer, Number of Positions	0	2
Total, Number of Positions	0	5
Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	237,461,000	310,767,000
Unrealized gains	12,820,000	14,629,000
Unrealized losses	0	0
Estimated fair value	250,281,000	325,396,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	0	0
12 Months or Longer, Fair Value	0	0
Total, Fair Value	0	0
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Longer, Unrealized Losses	0	0
Total, Unrealized Losses	0	0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	0	0
12 Months or Longer, Number of Positions	0	0
Total, Number of Positions	0	0
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	443,972,000	459,067,000
Unrealized gains	5,751,000	6,458,000
Unrealized losses	0	51,000
Estimated fair value	449,723,000	465,474,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	23,000	27,368,000
12 Months or Longer, Fair Value	0	0
Total, Fair Value	23,000	27,368,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	0	(51,000)
12 Months or Longer, Unrealized Losses	0	0
Total, Unrealized Losses	0	(51,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	2	3
12 Months or Longer, Number of Positions	0	0
Total, Number of Positions	2	3
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	0	0
Unrealized gains	0	0
Unrealized losses	0	0
Estimated fair value	0	0
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,210,000	8,935,000
Unrealized gains	2,832,000	2,021,000
Unrealized losses	88,000	76,000
Estimated fair value	13,954,000	10,880,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	468,000	645,000
12 Months or Longer, Fair Value	167,000	0
Total, Fair Value	635,000	645,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(6,000)	(76,000)
12 Months or Longer, Unrealized Losses	(82,000)	0
Total, Unrealized Losses	$ (88,000)	$ (76,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	1	2
12 Months or Longer, Number of Positions	1	0
Total, Number of Positions	2	2