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			63,352			63,352
Other comprehensive loss, net of tax				(82,735)		(82,735)
Cash dividends declared:
Common, $0.82 per share			(32,802)			(32,802)
Common stock issued under employee stock plan, including tax benefits of $1,183	657	11,122			293	12,072
Common stock issued under employee stock plan, including tax benefits of $1,183 (in shares)	670,109
Stock-based compensation		3,014				3,014
Balance at Sep. 30, 2013	$ 41,078	$ 392,549	$ 477,568	$ (28,401)	$ (17,115)	$ 865,679
Balance (in shares) at Sep. 30, 2013	40,296,042