Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 534,086	$ 604,182
Overnight investments		2,063,132	1,724,919
Investment securities available for sale		6,861,293	7,171,917
Investment securities held to maturity		255	518
Loans and Leases Receivable, Net Amount		20,033,774	18,564,999
FDIC Indemnification Asset		4,054	28,701	$ 93,397	$ 270,192
Income earned not collected		70,036	57,254
Deposits		26,930,755	25,678,577
Short-term borrowings		594,733	987,184
Long-term obligations		704,155	351,320
FDIC loss share payable		126,453	116,535
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		534,086	604,182
Overnight investments		2,063,132	1,724,919
Investment securities available for sale		6,861,293	7,171,917
Investment securities held to maturity		255	518
Loans held for sale		59,766	63,696
Loans and Leases Receivable, Net Amount		20,033,774	18,564,999
FDIC Indemnification Asset	[1]	4,054	28,701
Income earned not collected		70,036	57,254
Stock issued by Federal Home Loan Bank		37,511	39,113
Servicing Asset		19,351	16,688
Deposits		26,930,755	25,678,577
Short-term borrowings		594,733	987,184
Long-term obligations		704,155	351,320
FDIC loss share payable		126,453	116,535
Accrued interest payable		5,713	8,194
Derivative Liability, Fair Value, Gross Liability		1,429	4,337
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		534,086	604,182
Overnight investments		2,063,132	1,724,919
Investment securities available for sale		6,861,293	7,171,917
Investment securities held to maturity		265	544
Loans held for sale		59,766	63,696
Loans and Leases Receivable, Net Amount		19,353,325	18,046,497
FDIC Indemnification Asset	[1]	4,054	18,218
Income earned not collected		70,036	57,254
Stock issued by Federal Home Loan Bank		37,511	39,113
Servicing Asset		19,495	16,736
Deposits		26,164,472	25,164,683
Short-term borrowings		594,733	987,184
Long-term obligations		718,102	367,732
FDIC loss share payable		131,894	122,168
Accrued interest payable		5,713	8,194
Derivative Liability, Fair Value, Gross Liability		$ 1,429	$ 4,337

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