Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (27,131)	$ (29,882)	$ (82,160)	$ (89,894)
Income tax (expense) benefit	(25,868)	(27,765)	(81,554)	(72,114)
Investment securities gains, net	0	1,124	1,331	2,571
Salaries and other personnel expense	(193,749)	(187,328)	(560,115)	(550,799)
Net income available to common shareholders	44,229	37,188	134,399	82,704
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(112)	(112)	(336)	(336)
Income tax (expense) benefit	43	43	130	131
Net income available to common shareholders	(69)	(69)	(206)	(205)
Net Unrealized Gains (Losses) on Investment Securities Available for Sale [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit		(433)	(513)	(990)
Investment securities gains, net		1,124	1,331	2,571
Net income available to common shareholders		691	818	1,581
Post-Retirement Unfunded Health Benefit [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit		(28)	(56)	(38)
Salaries and other personnel expense		72	144	98
Net income available to common shareholders		$ 44	$ 88	$ 60