Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 539,741	$ 534,086
Overnight investments		1,872,594	2,063,132
Investment securities available for sale		7,006,580	6,861,293
Investment securities held to maturity		98	255
Net loans and leases		21,519,083	20,033,774
FDIC loss share receivable		4,172	4,054	$ 28,701	$ 93,397
Income earned not collected		79,839	70,036
Deposits		28,161,343	26,930,755
Short-term borrowings		603,487	594,733
Long-term obligations		832,942	704,155
FDIC shared-loss payable		97,008	126,453
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		539,741	534,086
Overnight investments		1,872,594	2,063,132
Investment securities available for sale		7,006,580	6,861,293
Investment securities held to maturity		98	255
Loans held for sale		74,401	59,766
Net loans and leases		21,519,083	20,033,774
FDIC loss share receivable		4,172	4,054
Income earned not collected		79,839	70,036
Federal Home Loan Bank stock		43,495	37,511
Mortgage servicing assets		20,415	19,351
Deposits		28,161,343	26,930,755
Short-term borrowings		603,487	594,733
Long-term obligations		832,942	704,155
FDIC shared-loss payable		97,008	126,453
Accrued interest payable		3,797	5,713
Interest rate swap	[1]	0	1,429
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		539,741	534,086
Overnight investments		1,872,594	2,063,132
Investment securities available for sale		7,006,580	6,861,293
Investment securities held to maturity		104	265
Loans held for sale		74,401	59,766
Net loans and leases		20,614,548	19,353,325
FDIC loss share receivable		4,172	4,054
Income earned not collected		79,839	70,036
Federal Home Loan Bank stock		43,495	37,511
Mortgage servicing assets		24,446	19,495
Deposits		28,135,698	26,164,472
Short-term borrowings		603,487	594,733
Long-term obligations		832,201	718,102
FDIC shared-loss payable		100,069	131,894
Accrued interest payable		3,797	5,713
Interest rate swap	[1]	$ 0	$ 1,429

[1] The interest rate swap agreement expired in June 2016.