Disclosures about fair value of assets and liabilities (Tables)

12 Months Ended

Dec. 31, 2012

Disclosures about Fair Value of Assets and Liabilities and Fair Value of Financial Instrument [Abstract]

Fair value measurements of assets and liabilities recognized on a recurring basis

				Quoted Prices in		Significant
				Active Markets		Other			Significant
				for Identical		Observable			Unobservable
				Assets		Inputs			Inputs
	Fair Value			(Level 1)		(Level 2)			(Level 3)
December 31, 2012
Available-for-sale securities
U.S. Treasury and federal agencies	$	51,779		$	—	$	51,779		$	—
State and municipal		172,905			—		172,905			—
Federal agency collateralized mortgage obligations		96,831			—		96,831			—
Federal agency mortgage-backed pools		159,204			—		159,204			—
Private labeled mortgage-backed pools		2,031			—		2,031			—
Corporate notes		51			—		51			—
Total available-for-sale securities		482,801			—		482,801			—
Hedged loans		81,018			—		81,018			—
Forward sale commitments		858			—		858			—
Interest rate swap agreements		(7,707	)		—		(7,707	)		—
Commitments to originate loans		—			—		—			—
December 31, 2011
Available-for-sale securities
U.S. Treasury and federal agencies	$	13,022		$	—	$	13,022		$	—
State and municipal		143,890			—		143,890			—
Federal agency collateralized mortgage obligations		91,122			—		91,122			—
Federal agency mortgage-backed pools		179,351			—		179,351			—
Private labeled mortgage-backed pools		3,636			—		3,636			—
Corporate notes		24			—		24			—
Total available-for-sale securities		431,045			—		431,045			—
Hedged loans		54,362			—		—			54,362
Forward sale commitments		662			—		—			662
Interest rate swap agreements		(7,102	)		—		—			(7,102	)
Commitments to originate loans		—			—		—			—

Schedule of fair value transfer among levels

	Quoted Prices
	in Active		Significant
	Markets for		Other			Significant
	Identical		Observable			Unobservable		Reason
	Assets		Inputs			Inputs		for
	(Level 1)		(Level 2)			(Level 3)		Transfer
Transfers to level:
Hedged loans	$	—	$	59,911		$	—	(a)
Forward sale commitments		—		510			—	(b)
Interest rate swap agreements		—		(6,464	)		—	(a)
Commitments to originate loans		—		(71	)		—	(b)
Total transfers to level	$	—	$	53,886		$	—

Reconciliation of the beginning and ending balances of recurring fair value measurements recognized in the accompanying condensed consolidated balance sheet using significant unobservable (Level 3) inputs

				Forward Sale			Interest Rate			Commitments to
	Hedged Loans			Commitments			Swaps			Originate Loans
Beginning balance December 31, 2011	$	54,362		$	662		$	(7,101	)	$	—
Total realized and unrealized gains and losses
Included in net income		(74	)		(152	)		74			(71	)
Included in other comprehensive income, gross		—			—			563			—
Purchases, issuances, and settlements		6,114			—			—			—
Principal payments		(491	)		—			—			—
Transfers out to Level 2		(59,911	)		(510	)		6,464			71
Ending balance December 31, 2012	$	—		$	—		$	—		$	—
				Forward Sale			Interest Rate			Commitments to
	Hedged Loans			Commitments			Swaps			Originate Loans
Beginning balance December 31, 2010	$	50,088		$	407		$	(3,415	)	$	—
Total realized and unrealized gains and losses
Included in net income		147			255			(147	)		—
Included in other comprehensive income, gross		—			—			(3,539	)		—
Purchases, issuances, and settlements		9,091			—			—			—
Principal payments		(4,964	)		—			—			—
Ending balance December 31, 2011	$	54,362		$	662		$	(7,101	)	$	—

Realized gains and losses included in net income for the periods in the condensed consolidated statements of income

	Years Ended December 31
	2012			2011			2010
Non Interest Income
Total gains and losses from:
Hedged loans	$	28		$	147		$	898
Fair value interest rate swap agreements		(28	)		(147	)		(898	)
Derivative loan commitments		196			255			(538	)
	$	196		$	255		$	(538	)

Other assets measured at fair value on a nonrecurring basis

			Quoted Prices in		Significant Other		Significant
			Active Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
	Fair Value		(Level 1)		(Level 2)		(Level 3)
December 31, 2012
Impaired loans	$	8,652	$	—	$	—	$	8,652
Mortgage servicing rights		5,145		—		—		5,145
December 31, 2011
Impaired loans	$	5,822	$	—	$	—	$	5,822
Mortgage servicing rights		4,193		—		—		4,193

Unobservable inputs in recurring and nonrecurring level 3 fair value measurements

	Fair Value at		Valuation		Range (Weighted
	December 31, 2012		Technique	Unobservable Inputs	Average)
Impaired loans		8,652	Collateral based measurement	Discount to reflect current market conditions and ultimate collectability	10% - 15% (12%)
Mortgage servicing rights		5,145	Discounted cashflows	Discount rate, Constant prepayment rate, Probably of default	10% -15% (12%), 4% - 7% (4.6%), 1% - 10% (4.5%)