Fair Value of Financial Assets and Liabilities (Details) (USD $)	3 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended										3 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012 Recurring [Member] Marketable Equity Securities [Member]	Sep. 30, 2011 Recurring [Member] Marketable Equity Securities [Member]	Sep. 30, 2012 Recurring [Member] Marketable Equity Securities [Member]	Sep. 30, 2011 Recurring [Member] Marketable Equity Securities [Member]	Sep. 30, 2012 Recurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2011 Recurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2012 Recurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2011 Recurring [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2012 Recurring [Member] Fair Value [Member]	Dec. 31, 2011 Recurring [Member] Fair Value [Member]	Sep. 30, 2012 Recurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2011 Recurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Sep. 30, 2012 Recurring [Member] Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2011 Recurring [Member] Significant Other Observable Inputs (Level 2) [Member]	Sep. 30, 2012 Recurring [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Recurring [Member] Significant Unobservable Inputs (Level 3) [Member]	Sep. 30, 2012 Nonrecurring [Member]	Dec. 31, 2011 Nonrecurring [Member]	Sep. 30, 2011 Nonrecurring [Member]	Sep. 30, 2012 Nonrecurring [Member] Fair Value [Member]	Dec. 31, 2011 Nonrecurring [Member] Fair Value [Member]	Sep. 30, 2012 Nonrecurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2011 Nonrecurring [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Sep. 30, 2012 Nonrecurring [Member] Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2011 Nonrecurring [Member] Significant Other Observable Inputs (Level 2) [Member]	Sep. 30, 2012 Nonrecurring [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Nonrecurring [Member] Significant Unobservable Inputs (Level 3) [Member]
Available-for-Sale [Abstract]
U.S. Treasury and government agencies											$ 26,655,000	$ 33,248,000	$ 0	$ 0	$ 26,655,000	$ 33,248,000	$ 0	$ 0
State and political subdivisions											105,364,000	72,144,000	0	0	105,364,000	72,144,000	0	0
U.S. government sponsored agency mortgage-backed securities											452,731,000	400,843,000	0	507,000	452,731,000	400,336,000	0	0
Marketable equity securities											36,480,000	21,163,000	36,269,000	20,675,000	0	277,000	211,000	211,000
Mortgage servicing rights											2,281,000	2,282,000	0	0	0	0	2,281,000	2,282,000
Assets measured-nonrecurring basis [Abstract]
Impaired loans (collateral dependent)																						5,927,000	7,898,000	0	0	0	0	5,927,000	7,898,000
Other real estate /assets owned																						7,222,000	16,362,000	0	0	0	0	7,222,000	16,362,000
Impaired loan (collateral dependent) [Abstract]
Impaired loans, fair value adjustments																			500,000	2,100,000	500,000
Other real estate owned [Abstract]
Other real estate /assets owned, fair value adjustment																			600,000	3,700,000	700,000
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			211,000	211,000	211,000	211,000	2,503,000	3,029,000	2,282,000	3,161,000
Total recognized gains (losses) Included in net income			0	0	0	0	(257,000)	(763,000)	(85,000)	(957,000)
Issues			0	0	0	0	170,000	127,000	510,000	378,000
Settlements			0	0	0	0	(135,000)	7,000	(426,000)	(182,000)
Ending balance			211,000		211,000		2,281,000	2,400,000	2,281,000	2,400,000
Total recognized gains (losses) Included in net income			0	0	0	0	(257,000)	(763,000)	(85,000)	(957,000)
Total gains, noninterest income	(392,000)	(511,000)
Total gains, noninterest expense	$ 0	$ 0