Loans and Allowance for Loan Losses (Schedule Of Allowances For Loan Losses And Recorded Investment In Loans) (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Allowance for loan losses:
Beginning balance, allowance	$ 257,764,000	$ 253,514,000	$ 249,268,000	$ 251,758,000	$ 251,758,000
Charge-offs	(21,504,000)	(19,663,000)	(36,126,000)	(32,398,000)
Recoveries	3,675,000	3,984,000	14,017,000	9,801,000
Provision for loan losses	11,790,000	10,260,000	24,566,000	18,934,000
Ending balance, allowance	251,725,000	248,095,000	251,725,000	248,095,000	249,268,000
Ending balance: individually evaluated for impairment, allowance	14,932,000	12,650,000	14,932,000	12,650,000
Ending balance: collectively evaluated for impairment, allowance	236,793,000	235,445,000	236,793,000	235,445,000
Total loans	25,156,773,000	24,456,550,000	25,156,773,000	24,456,550,000	24,812,795,000
Ending balance: individually evaluated for impairment, loans	189,025,000	228,215,000	189,025,000	228,215,000
Ending balance: collectively evaluated for impairment, loans	24,967,748,000	24,228,335,000	24,967,748,000	24,228,335,000
Purchased credit-impaired loans	0	0		0
Allowance for purchased credit-impaired loans	0	0		0
Deferred fees and costs, net	22,700,000	26,000,000	22,700,000	26,000,000	25,300,000
Commercial & Industrial
Allowance for loan losses:
Beginning balance, allowance	134,745,000	127,096,000	126,803,000	125,778,000	125,778,000
Charge-offs	(15,770,000)	(12,642,000)	(23,786,000)	(19,535,000)
Recoveries	1,635,000	1,458,000	3,995,000	3,282,000
Provision for loan losses	9,725,000	7,525,000	23,323,000	13,912,000
Ending balance, allowance	130,335,000	123,437,000	130,335,000	123,437,000	126,803,000
Ending balance: individually evaluated for impairment, allowance	9,474,000	7,226,000	9,474,000	7,226,000
Ending balance: collectively evaluated for impairment, allowance	120,861,000	116,211,000	120,861,000	116,211,000
Total loans	12,275,472,000	11,742,945,000	12,275,472,000	11,742,945,000
Ending balance: individually evaluated for impairment, loans	107,544,000	122,889,000	107,544,000	122,889,000
Ending balance: collectively evaluated for impairment, loans	12,167,928,000	11,620,056,000	12,167,928,000	11,620,056,000
Commercial Real Estate
Allowance for loan losses:
Beginning balance, allowance	73,991,000	78,314,000	74,998,000	81,816,000	81,816,000
Charge-offs	(523,000)	(1,299,000)	(2,446,000)	(3,207,000)
Recoveries	480,000	759,000	6,964,000	3,648,000
Provision for loan losses	1,257,000	(247,000)	(4,311,000)	(4,730,000)
Ending balance, allowance	75,205,000	77,527,000	75,205,000	77,527,000	74,998,000
Ending balance: individually evaluated for impairment, allowance	4,687,000	4,386,000	4,687,000	4,386,000
Ending balance: collectively evaluated for impairment, allowance	70,518,000	73,141,000	70,518,000	73,141,000
Total loans	6,644,171,000	7,422,234,000	6,644,171,000	7,422,234,000
Ending balance: individually evaluated for impairment, loans	53,805,000	73,638,000	53,805,000	73,638,000
Ending balance: collectively evaluated for impairment, loans	6,590,366,000	7,348,596,000	6,590,366,000	7,348,596,000
Consumer
Allowance for loan losses:
Beginning balance, allowance	49,028,000	48,104,000	47,467,000	44,164,000	44,164,000
Charge-offs	(5,211,000)	(5,722,000)	(9,894,000)	(9,656,000)
Recoveries	1,560,000	1,767,000	3,058,000	2,871,000
Provision for loan losses	808,000	2,982,000	5,554,000	9,752,000
Ending balance, allowance	46,185,000	47,131,000	46,185,000	47,131,000	$ 47,467,000
Ending balance: individually evaluated for impairment, allowance	771,000	1,038,000	771,000	1,038,000
Ending balance: collectively evaluated for impairment, allowance	45,414,000	46,093,000	45,414,000	46,093,000
Total loans	6,237,130,000	5,291,371,000	6,237,130,000	5,291,371,000
Ending balance: individually evaluated for impairment, loans	27,676,000	31,688,000	27,676,000	31,688,000
Ending balance: collectively evaluated for impairment, loans	$ 6,209,454,000	$ 5,259,683,000	$ 6,209,454,000	$ 5,259,683,000