Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity at beginning of year	$ 381,724us-gaap_StockholdersEquity	$ 346,712us-gaap_StockholdersEquity	$ 319,061us-gaap_StockholdersEquity
Net income	29,717us-gaap_NetIncomeLoss	36,588us-gaap_NetIncomeLoss	31,919us-gaap_NetIncomeLoss
Other comprehensive income	1,740	13,047	9,092
Cash dividends paid to shareholders	(14,947)us-gaap_DividendsCommonStockCash	(14,943)us-gaap_DividendsCommonStockCash	(14,886)us-gaap_DividendsCommonStockCash
Issuance of common stock	1,262	320	1,526
Shareholders' equity at end of year:	$ 399,496us-gaap_StockholdersEquity	$ 381,724us-gaap_StockholdersEquity	$ 346,712us-gaap_StockholdersEquity

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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