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, 2014	$ 2,334,246	$ 144,784	$ 484,155	$ 1,229,075	$ 426,648	$ (16,562)	$ 62,093	$ 4,053
Net income	137,337				135,408			1,929
Other comprehensive income (loss)	(13,304)						(13,304)
Distributions to non-controlling interest	(543)							(543)
Purchase of treasury stock	(3,575)					(3,575)
Accelerated stock repurchase agreement	(100,000)			40,000		(140,000)
Issuance of stock under purchase and equity compensation plans	1,890			(14,682)		16,572
Net tax benefit related to equity compensation plans	1,662			1,662
Stock-based compensation	5,252			5,252
Cash dividends per share, Common Stock, Cash	(43,105)				(43,105)
Dividends per share, Preferred Stock, Cash	(4,500)				(4,500)
Balance at Jun. 30, 2015	2,315,360	144,784	484,155	1,261,307	514,451	(143,565)	48,789	5,439
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	135,330				135,267			63
Other comprehensive income (loss)	101,954						101,954
Distributions to non-controlling interest	(586)							(586)
Purchase of treasury stock	(37,462)					(37,462)
Issuance of stock under purchase and equity compensation plans	(2)			(11,873)		11,871
Net tax benefit related to equity compensation plans	1,904			1,904
Stock-based compensation	6,287			6,287
Cash dividends per share, Common Stock, Cash	(43,522)				(43,522)
Dividends per share, Preferred Stock, Cash	(4,500)				(4,500)
Balance at Jun. 30, 2016	$ 2,526,821	$ 144,784	$ 489,862	$ 1,333,995	$ 470,558	$ (51,707)	$ 134,424	$ 4,905