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, 2015	$ 2,367,418	$ 144,784	$ 489,862	$ 1,337,677	$ 383,313	$ (26,116)	$ 32,470	$ 5,428
Net income	65,522				65,374			148
Other comprehensive income (loss)	70,459						70,459
Distributions to non-controlling interest	(322)							(322)
Purchase of treasury stock	(36,432)					(36,432)
Issuance of stock under purchase and equity compensation plans	0			(9,895)		9,895
Net tax benefit related to equity compensation plans	1,236			1,236
Stock-based compensation	3,411			3,411
Cash dividends per share, Common Stock, Cash	(21,760)				(21,760)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2016	2,447,282	144,784	489,862	1,332,429	424,677	(52,653)	102,929	5,254
Balance at Dec. 31, 2016	2,501,132	144,784	510,015	1,552,454	292,849	(15,294)	10,975	5,349
Adoption of ASU 2016-09	1,297			3,441	(2,144)
Net income	71,702				71,504			198
Other comprehensive income (loss)	19,437						19,437
Distributions to non-controlling interest	(685)							(685)
Purchase of treasury stock	(7,284)					(7,284)
Issuance of stock under purchase and equity compensation plans	(6)			(14,996)		14,990
Stock-based compensation	3,135			3,135
Cash dividends per share, Common Stock, Cash	(22,913)				(22,913)
Dividends per share, Preferred Stock, Cash	(2,250)				(2,250)
Balance at Mar. 31, 2017	$ 2,563,565	$ 144,784	$ 510,015	$ 1,544,034	$ 337,046	$ (7,588)	$ 30,412	$ 4,862