Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (31,130)	$ (28,138)
Loss on early extinguishment of debt	(4,735)	0
Income tax (expense) benefit	(31,199)	(31,849)
Investment securities gains, net	67	725
Salaries and other personnel expense	(188,233)	(178,908)
Net income available to common shareholders	49,972	51,404
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(76)	(112)
Loss on early extinguishment of debt	(197)	0
Income tax (expense) benefit	105	43
Net income available to common shareholders	(168)	(69)
Net Unrealized Gains (Losses) on Investment Securities Available for Sale [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	(26)	(281)
Investment securities gains, net	67	725
Net income available to common shareholders	41	444
Post-Retirement Unfunded Health Benefit [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	(36)	(16)
Salaries and other personnel expense	94	42
Net income available to common shareholders	$ 58	$ 26