Fair Value of Financial Instruments, Part 1 (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Securities available-for sale [Abstract]
U.S. government-sponsored enterprises			$ 0
Total securities available for sale	878,188,000	878,188,000	912,092,000
Other real estate owned (ORE) [Abstract]
Other real estate owned, commercial real estate	6,100,000	6,100,000	4,800,000
Other real estate owned, residential real estate properties	4,200,000	4,200,000	3,900,000
Valuation charge on other real estate owned	941,000	1,100,000	1,100,000
Impaired Loans [Abstract]
Impaired loans	25,365,000	25,365,000	26,073,000
Collateral dependent impaired loans	7,900,000	7,900,000	10,800,000
Gross charge offs, commercial impaired loans	20,000	170,000	2,500,000
Gross charge offs, residential impaired loans	109,000	276,000	1,700,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available-for sale [Abstract]
Total securities available for sale	10,000	10,000	10,000
Significant Other Observable Inputs (Level 2) [Member]
Securities available-for sale [Abstract]
Total securities available for sale	878,178,000	878,178,000	912,082,000
Significant Unobservable Inputs (Level 3) [Member]
Securities available-for sale [Abstract]
Total securities available for sale	0	0	0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities available-for sale [Abstract]
U.S. government-sponsored enterprises	0	0	0
State and political subdivisions	0	0	0
Mortgage-backed securities and collateralized mortgage obligations - residential	0	0	0
Corporate bonds	0	0	0
Small Business Administration-guaranteed participation securities	0	0	0
Mortgage-backed securities and collateralized mortgage obligations - commercial	0	0
Other securities	10,000	10,000	10,000
Total securities available for sale	10,000	10,000	10,000
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Securities available-for sale [Abstract]
U.S. government-sponsored enterprises	188,133,000	188,133,000	263,108,000
State and political subdivisions	12,159,000	12,159,000	26,457,000
Mortgage-backed securities and collateralized mortgage obligations - residential	504,793,000	504,793,000	518,776,000
Corporate bonds	53,053,000	53,053,000	26,529,000
Small Business Administration-guaranteed participation securities	108,665,000	108,665,000	76,562,000
Mortgage-backed securities and collateralized mortgage obligations - commercial	10,725,000	10,725,000
Other securities	650,000	650,000	650,000
Total securities available for sale	878,178,000	878,178,000	912,082,000
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Securities available-for sale [Abstract]
U.S. government-sponsored enterprises	0	0
State and political subdivisions	0	0	0
Mortgage-backed securities and collateralized mortgage obligations - residential	0	0	0
Corporate bonds	0	0	0
Small Business Administration-guaranteed participation securities	0	0
Mortgage-backed securities and collateralized mortgage obligations - commercial	0	0
Other securities	0	0	0
Total securities available for sale	0	0	0
Recurring [Member] | Carrying Value [Member]
Securities available-for sale [Abstract]
U.S. government-sponsored enterprises	188,133,000	188,133,000	263,108,000
State and political subdivisions	12,159,000	12,159,000	26,457,000
Mortgage-backed securities and collateralized mortgage obligations - residential	504,793,000	504,793,000	518,776,000
Corporate bonds	53,053,000	53,053,000	26,529,000
Small Business Administration-guaranteed participation securities	108,665,000	108,665,000	76,562,000
Mortgage-backed securities and collateralized mortgage obligations - commercial	10,725,000	10,725,000
Other securities	660,000	660,000	660,000
Total securities available for sale	878,188,000	878,188,000	912,092,000
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Other real estate owned (ORE) [Abstract]
Other real estate owned	0	0	0
Impaired Loans [Abstract]
Commercial real estate	0	0	0
Real estate mortgage - 1 to 4 family: First mortgages	0	0	0
Home Equity Loans	0	0	0
Home Equity Lines of Credit	0	0	0
Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Other real estate owned (ORE) [Abstract]
Other real estate owned	0	0	0
Impaired Loans [Abstract]
Commercial real estate	0	0	0
Real estate mortgage - 1 to 4 family: First mortgages	0	0	0
Home Equity Loans	0	0	0
Home Equity Lines of Credit	0	0	0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Other real estate owned (ORE) [Abstract]
Other real estate owned	10,345,000	10,345,000	8,705,000
Impaired Loans [Abstract]
Commercial real estate	2,303,000	2,303,000	4,690,000
Real estate mortgage - 1 to 4 family: First mortgages	4,849,000	4,849,000	5,421,000
Home Equity Loans	66,000	66,000	67,000
Home Equity Lines of Credit	639,000	639,000	581,000
Nonrecurring [Member] | Carrying Value [Member]
Other real estate owned (ORE) [Abstract]
Other real estate owned	10,345,000	10,345,000	8,705,000
Impaired Loans [Abstract]
Commercial real estate	2,303,000	2,303,000	4,690,000
Real estate mortgage - 1 to 4 family: First mortgages	4,849,000	4,849,000	5,421,000
Home Equity Loans	66,000	66,000	67,000
Home Equity Lines of Credit	$ 639,000	$ 639,000	$ 581,000