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, 2011	$ 37,795	$ 313,501	$ 411,805	$ 29,165	$ (17,683)	$ 774,583
Balance (in shares) at Dec. 31, 2011	36,986,409
Net income			58,264			58,264
Other comprehensive income, net of tax				36,971		36,971
Dividends declared:
Common, $0.79 per share			(31,157)			(31,157)
Common stock issued under employee stock plan, including tax benefits of $1,013	445	7,511			210	8,166
Common stock issued under Employee stock plan, including tax benefits of $1,013 (in shares)	455,224
Stock-based compensation		2,855				2,855
Common stock issuance	2,130	52,787				54,917
Common stock issuance (in shares)	2,129,800					2,130,000
Balance at Sep. 30, 2012	$ 40,370	$ 376,654	$ 438,912	$ 66,136	$ (17,473)	$ 904,599
Balance (in shares) at Sep. 30, 2012	39,571,433