CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2012	$ 40,421	$ 378,413	$ 447,018	$ 54,334	$ (17,408)	$ 902,778
Balance (in shares) at Dec. 31, 2012	39,625,933
Net income			41,363			41,363
Other comprehensive income, net of tax				(82,050)		(82,050)
Cash dividends declared:
Common, $0.54 per share			(21,533)			(21,533)
Common stock issued under employee stock plan, including tax benefits of $666	460	6,613			293	7,366
Common stock issued under employee stock plan, including tax benefits of $666 (in shares)	473,082
Stock-based compensation		2,107				2,107
Balance at Jun. 30, 2013	$ 40,881	$ 387,133	$ 466,848	$ (27,716)	$ (17,115)	$ 850,031
Balance (in shares) at Jun. 30, 2013	40,099,015