Other Comprehensive Income (Loss) (Reclassifications out of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (34,413)	$ (30,944)	$ (66,887)	$ (62,073)
Loss on early extinguishment of debt, net	0	0	0	(4,735)
Income tax (expense) benefit	(41,788)	(33,574)	(75,635)	(64,773)
Investment securities gains, net	(1)	0	7,667	67
Salaries and other personnel expense	(191,747)	(188,611)	(389,133)	(376,844)
Net income available to common shareholders	73,444	57,898	142,742	107,870
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Net unrealized gains (losses) on cash flow hedges
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	(65)	(64)	(130)	(140)
Loss on early extinguishment of debt, net			0	(197)
Income tax (expense) benefit	25	25	50	130
Net income available to common shareholders	(40)	(39)	(80)	(207)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Net unrealized gains (losses) on investment securities available for sale
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	0	0	(2,952)	(26)
Investment securities gains, net	(1)	0	7,667	67
Net income available to common shareholders	(1)	0	4,715	41
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) | Post-retirement unfunded health benefit
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit	(8)	(4)	(16)	(40)
Salaries and other personnel expense	20	10	40	104
Net income available to common shareholders	$ 12	$ 6	$ 24	$ 64