Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014	$ 7,369,530	$ 1,004,011	$ 4,723,855	$ 1,769,705	$ (128,041)
Balance (in shares) at Dec. 31, 2014			203,014,903
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	92,025			92,025
Other comprehensive income, net of tax	13,132				13,132
Subordinated debt converted to preferred stock	15	$ 21	$ (6)
Net activity under employee plans and related tax benefits	4,707		$ 4,707
Net activity under employee plans and related tax benefits, shares			178,088
Dividends on preferred stock	(16,746)			(16,746)
Dividends on common stock	(8,176)			(8,176)
Change in deferred compensation	(189)			(189)
Balance at Mar. 31, 2015	7,454,298	$ 1,004,032	$ 4,728,556	1,836,619	(114,909)
Balance (in shares) at Mar. 31, 2015			203,192,991
Balance at Dec. 31, 2015	$ 7,507,519	828,490	$ 4,766,731	1,966,910	(54,612)
Balance (in shares) at Dec. 31, 2015	204,417,093		204,417,093
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	$ 90,437			90,437
Other comprehensive income, net of tax	42,959				42,959
Net activity under employee plans and related tax benefits	10,899		$ 10,899
Net activity under employee plans and related tax benefits, shares			126,614
Dividends on preferred stock	(11,660)			(11,660)
Dividends on common stock	(12,350)			(12,350)
Change in deferred compensation	(2,067)			(2,067)
Balance at Mar. 31, 2016	$ 7,625,737	$ 828,490	$ 4,777,630	$ 2,031,270	$ (11,653)
Balance (in shares) at Mar. 31, 2016	204,543,707		204,543,707