Loans and Allowance for Loan Losses (Schedule Of Allowances For Loan Losses And Recorded Investment In Loans) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance, allowance	$ 251,758,000	$ 252,496,000	$ 252,496,000
Charge-offs	(12,735,000)	(11,315,000)
Recoveries	5,817,000	3,958,000
Provision for loan losses	8,674,000	9,377,000
Ending balance, allowance	253,514,000	254,516,000	251,758,000
Ending balance: individually evaluated for impairment, allowance	19,707,000	32,973,000
Ending balance: collectively evaluated for impairment, allowance	233,807,000	221,543,000
Total loans	24,284,188,000	22,787,534,000	23,882,382,000
Ending balance: individually evaluated for impairment, loans	234,756,000	297,785,000
Ending balance: collectively evaluated for impairment, loans	24,049,432,000	22,489,749,000
Purchased credit-impaired loans	0	0	0
Allowance for purchased credit-impaired loans	0	0	0
Deferred fees and costs, net	25,700,000	29,300,000	26,000,000
Commercial Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance, allowance	81,816,000	87,133,000	87,133,000
Charge-offs	(1,908,000)	(1,822,000)
Recoveries	2,889,000	1,293,000
Provision for loan losses	(4,483,000)	(2,047,000)
Ending balance, allowance	78,314,000	84,557,000	81,816,000
Ending balance: individually evaluated for impairment, allowance	6,917,000	17,603,000
Ending balance: collectively evaluated for impairment, allowance	71,397,000	66,954,000
Total loans	7,459,223,000	7,613,635,000
Ending balance: individually evaluated for impairment, loans	79,203,000	136,826,000
Ending balance: collectively evaluated for impairment, loans	7,380,020,000	7,476,809,000
Commercial and Industrial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance, allowance	125,778,000	122,989,000	122,989,000
Charge-offs	(6,893,000)	(5,525,000)
Recoveries	1,824,000	1,264,000
Provision for loan losses	6,387,000	6,150,000
Ending balance, allowance	127,096,000	124,878,000	125,778,000
Ending balance: individually evaluated for impairment, allowance	11,085,000	14,033,000
Ending balance: collectively evaluated for impairment, allowance	116,011,000	110,845,000
Total loans	11,740,766,000	10,809,472,000
Ending balance: individually evaluated for impairment, loans	120,470,000	123,557,000
Ending balance: collectively evaluated for impairment, loans	11,620,296,000	10,685,915,000
Retail [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance, allowance	44,164,000	42,374,000	42,374,000
Charge-offs	(3,934,000)	(3,968,000)
Recoveries	1,104,000	1,401,000
Provision for loan losses	6,770,000	5,274,000
Ending balance, allowance	48,104,000	45,081,000	$ 44,164,000
Ending balance: individually evaluated for impairment, allowance	1,705,000	1,337,000
Ending balance: collectively evaluated for impairment, allowance	46,399,000	43,744,000
Total loans	5,084,199,000	4,364,427,000
Ending balance: individually evaluated for impairment, loans	35,083,000	37,402,000
Ending balance: collectively evaluated for impairment, loans	$ 5,049,116,000	$ 4,327,025,000