Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		$ 514,404		$ 604,182
Overnight investments		1,703,341		1,724,919
Investment securities available for sale		7,350,194		7,171,917
Investment securities held to maturity		351		518
Loans held for sale		85,040		63,696
Loans and Leases Receivable, Net Amount		19,311,868		18,564,999
FDIC Indemnification Asset		5,808	$ 21,340	28,701	$ 49,959	$ 74,784	$ 93,397
Income earned not collected		66,729		57,254
Mortgage servicing rights		18,162	$ 16,436	16,688	$ 0	$ 0	$ 16
Deposits		26,511,896		25,678,577
FDIC loss share payable		122,038		116,535
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		514,404		604,182
Overnight investments		1,703,341		1,724,919
Investment securities available for sale		7,350,194		7,171,917
Investment securities held to maturity		351		518
Loans held for sale		85,040		63,696
Loans and Leases Receivable, Net Amount		19,311,868		18,564,999
FDIC Indemnification Asset	[1]	5,808		28,701
Income earned not collected		66,729		57,254
Stock issued by Federal Home Loan Bank		27,736		39,113
Preferred stock and other acquired financial assets		3,016		13,689
Mortgage servicing rights		18,162		16,688
Deposits		26,511,896		25,678,577
Short-term borrowings		723,225		987,184
Long-term obligations		475,568		351,320
FDIC loss share payable		122,038		116,535
Accrued interest payable		5,835		8,194
Interest rate swap		3,052		4,337
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks		514,404		604,182
Overnight investments		1,703,341		1,724,919
Investment securities available for sale		7,350,194		7,171,917
Investment securities held to maturity		365		544
Loans held for sale		85,040		63,696
Loans and Leases Receivable, Net Amount		18,755,676		18,046,497
FDIC Indemnification Asset	[1]	5,808		18,218
Income earned not collected		66,729		57,254
Stock issued by Federal Home Loan Bank		27,736		39,113
Preferred stock and other acquired financial assets		3,061		14,708
Mortgage servicing rights		20,078		16,736
Deposits		25,915,474		25,164,683
Short-term borrowings		723,225		987,184
Long-term obligations		493,715		367,732
FDIC loss share payable		128,049		122,168
Accrued interest payable		5,835		8,194
Interest rate swap		$ 3,052		$ 4,337

[1] (1) At June 30, 2015, the carrying value of the FDIC receivable approximates the fair value due to the short term nature of the majority of loss share agreements. At December 31, 2014, the fair value of the FDIC receivable is estimated based on discounted future cash flows using current discount rates and excludes receivable related to accretable yield to be amortized in prospective periods.