Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2011	$ 1,033,556	$ 94,654	$ 834,033	$ 89,865	$ 15,004
Net income	48,929			48,929
Other comprehensive income (loss)	7,338				7,338
Dividends - common stock	(17,023)			(17,023)
Common stock issued	123	10	113
Common stock repurchased	(686)	(55)	(631)
Stock based compensation expense	1,344		1,344
Stock activity under incentive comp plans	146	78	169	(101)
Balance at Jun. 30, 2012	1,073,727	94,687	835,028	121,670	22,342
Balance at Dec. 31, 2012	1,194,565	101,179	916,918	146,667	29,801
Net income	52,423			52,423
Other comprehensive income (loss)	(54,822)				(54,822)
Dividends - common stock	(20,211)			(20,211)
Common stock issued	139	11	128
Common stock repurchased	(7,686)	(589)	(7,097)
Stock based compensation expense	2,136		2,136
Stock activity under incentive comp plans	434	280	306	(152)
Balance at Jun. 30, 2013	$ 1,166,978	$ 100,881	$ 912,391	$ 178,727	$ (25,021)