Investment Securities (Summary Of Debt Securities By Contractual Maturity) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Investments, Debt and Equity Securities [Abstract]
Available for Sale, Amortized Cost - Due in one year or less	$ 9,741
Available for Sale, Amortized Cost - Due after one year through five years	70,449
Available for Sale, Amortized Cost - Due after five through ten years	48,022
Available for Sale, Amortized Cost - Due after ten years	2,916,990
Available for Sale, Amortized Cost - Total debt securities	3,045,202
Available for Sale, Fair Value - Due in one year or less	8,067
Available for Sale, Fair Value - Due after one year through five years	74,687
Available for Sale, Fair Value - Due after five through ten years	50,075
Available for Sale, Fair Value - Due after ten years	2,979,230
Available for Sale, Fair Value - Total debt securities	3,112,059
Held to Maturity, Amortized Cost - Due in one year or less	15,113
Held to Maturity, Amortized Cost - Due after one year through five years	11,619
Held to Maturity, Amortized Cost - Due after five through ten years	225,637
Held to Maturity, Amortized Cost - Due after ten years	2,889,791
Held to Maturity, Amortized Cost - Total debt securities	3,142,160
Held to Maturity, Fair Value - Due in one year or less	15,119
Held to Maturity, Fair Value - Due after one year through five years	12,204
Held to Maturity, Fair Value - Due after five through ten years	239,891
Held to Maturity, Fair Value - Due after ten years	3,054,103
Held to Maturity, Fair Value - Total debt securities	$ 3,321,317

Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 7

-Footnote 2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 20

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.