Consolidated Statements Of Changes In Equity (USD $) In Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-Controlling Interest [Member]
Balance at Dec. 31, 2013	$ 2,214,397	$ 0	$ 481,224	$ 1,279,948	$ 449,836	$ (10,097)	$ 9,731	$ 3,755
Net income	64,121				64,313			(192)
Other comprehensive income (loss)	30,768						30,768
Distributions to non-controlling interest	(431)							(431)
Issuance of preferred stock	0
Purchase of treasury stock	(20,900)					(20,900)
Issuance of stock under purchase and equity compensation plans	4,085			(2,897)		6,982
Net tax benefit related to equity compensation plans	800			800
Stock-based compensation	2,261			2,261
Issuance of nonvested stock awards	0			(6,822)		6,822
Cash dividends per share, Common Stock, Cash	(21,590)				(21,590)
Balance at Mar. 31, 2014	2,273,511	0	481,224	1,273,290	492,559	(17,193)	40,499	3,132
Balance at Dec. 31, 2014	2,334,246	144,784	484,155	1,229,075	426,648	(16,562)	62,093	4,053
Net income	62,014				61,055			959
Other comprehensive income (loss)	29,624						29,624
Distributions to non-controlling interest	(219)							(219)
Purchase of treasury stock	(1,718)					(1,718)
Issuance of stock under purchase and equity compensation plans	1,865			(1,312)		3,177
Net tax benefit related to equity compensation plans	857			857
Stock-based compensation	2,740			2,740
Issuance of nonvested stock awards	0			(8,235)		8,235
Cash dividends per share, Common Stock, Cash	(21,752)				(21,752)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2015	$ 2,405,407	$ 144,784	$ 484,155	$ 1,223,125	$ 463,701	$ (6,868)	$ 91,717	$ 4,793