Consolidated Statements of Shareholders' Equity $ in Thousands	USD ($)
Shareholders' equity at beginning of year at Dec. 31, 2012	$ 346,712
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,588
Other comprehensive income (loss)	13,047
Cash dividends paid to shareholders	(14,943)
Issuance of common stock	320
Shareholders' equity at end of year: at Dec. 31, 2013	381,724
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	29,717
Other comprehensive income (loss)	1,740
Cash dividends paid to shareholders	(14,947)
Issuance of common stock	1,262
Shareholders' equity at end of year: at Dec. 31, 2014	399,496
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,283
Other comprehensive income (loss)	(14,372)
Cash dividends paid to shareholders	(15,003)
Issuance of common stock	1,094
Shareholders' equity at end of year: at Dec. 31, 2015	$ 394,498