Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Amortized cost of securities available-for-sale	$ 1,299,980	$ 1,222,143
Fair value of securities held-to-maturity	$ 143,490	$ 187,402
Preferred stock, shares authorized	200,000us-gaap_PreferredStockSharesAuthorized	200,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued	0us-gaap_PreferredStockSharesOutstanding	0us-gaap_PreferredStockSharesOutstanding
Preferred stock per share liquidation preference	$ 0	$ 0
Common stock, no par value	$ 0us-gaap_CommonStockNoParValue	$ 0us-gaap_CommonStockNoParValue
Common stock, shares authorized	20,000,000us-gaap_CommonStockSharesAuthorized	20,000,000us-gaap_CommonStockSharesAuthorized
Common stock stock, shares issued	16,150,888us-gaap_CommonStockSharesIssued	16,150,941us-gaap_CommonStockSharesIssued
Treasury stock, shares	758,489us-gaap_TreasuryStockShares	738,989us-gaap_TreasuryStockShares

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Face amount per share of no-par value common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Fair value of investments in debt securities classified as held-to-maturity.

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