Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (27,162)	$ (29,436)	$ (55,029)	$ (60,012)
Income tax (expense) benefit	(27,078)	(27,371)	(55,686)	(44,350)
Investment securities gains, net	0	1,403	1,331	1,448
Salaries and other personnel expense	(182,205)	(181,186)	(366,365)	(363,472)
Net income available to common shareholders	44,313	30,717	90,170	45,515
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(112)	(112)	(224)	(224)
Income tax (expense) benefit	44	45	87	88
Net income available to common shareholders	(68)	(67)	(137)	(136)
Net Unrealized Gains (Losses) on Investment Securities Available for Sale [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	0	(541)	(513)	(557)
Investment securities gains, net	0	1,403	1,331	1,448
Net income available to common shareholders	0	862	818	891
Post-Retirement Unfunded Health Benefit [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	(28)	(7)	(56)	(10)
Salaries and other personnel expense	72	0	144	26
Net income available to common shareholders	$ 44	$ (7)	$ 88	$ 16