Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Jun. 30, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 400,993			$ 533,599
Overnight investments	707,352			859,324
Investment securities available for sale	5,648,094			5,387,703
Investment securities held to maturity	607			907
Loans held for sale	43,612			47,271
Loans and Leases Receivable, Net Amount	13,601,886			12,900,330
FDIC Indemnification Asset	45,140		49,959	93,397		100,553	158,013	270,192
Income earned not collected	48,511			48,390
Deposits	18,406,941			17,874,066
FDIC loss share payable	116,924			109,378
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	400,993			533,599
Overnight investments	707,352			859,324
Investment securities available for sale	5,648,094			5,387,703
Investment securities held to maturity	607			907
Loans held for sale	43,612			47,271
Loans and Leases Receivable, Net Amount	13,601,886			12,900,330
FDIC Indemnification Asset	45,140	[1]		93,397	[1]
Income earned not collected	48,511			48,390
Stock issued by Federal Home Loan Bank	32,309			40,819
Preferred stock and other acquired financial assets	13,390			33,564
Deposits	18,406,941			17,874,066
Short-term borrowings	798,169			511,418
Long-term obligations	313,768			510,769
FDIC loss share payable	116,924			109,378
Accrued interest payable	5,303			6,737
Interest rate swap	4,984			7,220
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	400,993			533,599
Overnight investments	707,352			859,324
Investment securities available for sale	5,648,094			5,387,703
Investment securities held to maturity	638			974
Loans held for sale	44,172			47,956
Loans and Leases Receivable, Net Amount	13,091,758			12,545,537
FDIC Indemnification Asset	22,788	[1]		38,438	[1]
Income earned not collected	48,511			48,390
Stock issued by Federal Home Loan Bank	32,309			40,819
Preferred stock and other acquired financial assets	14,388			34,786
Deposits	17,943,397			17,898,570
Short-term borrowings	798,169			511,418
Long-term obligations	326,743			526,037
FDIC loss share payable	124,330			111,941
Accrued interest payable	5,303			6,737
Interest rate swap	$ 4,984			$ 7,220

[1] The fair value of the FDIC receivable excludes amortization expected to be recognized in prospective periods.