Investment Securities (Summary of Available for Sale Investment Securities by Maturity Groupings) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Amortized Cost	$ 9,065,853	$ 7,164,763
Fair Value	9,278,066	7,294,303
U.S. Government and Federal Agency Obligations [Member]
Amortized Cost	327,915	434,878
Fair Value	360,102	455,537
U.S. Government and Federal Agency Obligations [Member] \| Available-for-Sale Securities, Maturity within 1 Year [Member]
Amortized Cost	7,760
Fair Value	8,115
U.S. Government and Federal Agency Obligations [Member] \| Available-for-Sale Securities, Maturity After 1 But within 5 Years [Member]
Amortized Cost	157,825
Fair Value	172,119
U.S. Government and Federal Agency Obligations [Member] \| Available-for-Sale securities, Maturity After 5 But within 10 Years [Member]
Amortized Cost	162,330
Fair Value	179,868
Government-Sponsored Enterprise Obligations [Member]
Amortized Cost	260,361	200,061
Fair Value	264,550	201,895
Government-Sponsored Enterprise Obligations [Member] \| Available-for-Sale Securities, Maturity within 1 Year [Member]
Amortized Cost	75,434
Fair Value	76,251
Government-Sponsored Enterprise Obligations [Member] \| Available-for-Sale Securities, Maturity After 1 But within 5 Years [Member]
Amortized Cost	110,448
Fair Value	113,520
Government-Sponsored Enterprise Obligations [Member] \| Available-for-Sale securities, Maturity After 5 But within 10 Years [Member]
Amortized Cost	49,504
Fair Value	49,885
Government-Sponsored Enterprise Obligations [Member] \| Available-for-Sale, Maturity After 10 Years [Member]
Amortized Cost	24,975
Fair Value	24,894
State and Municipal Obligations [Member]
Amortized Cost	1,241,610	1,117,020
Fair Value	1,259,384	1,119,485
State and Municipal Obligations [Member] \| Available-for-Sale Securities, Maturity within 1 Year [Member]
Amortized Cost	102,321
Fair Value	103,355
State and Municipal Obligations [Member] \| Available-for-Sale Securities, Maturity After 1 But within 5 Years [Member]
Amortized Cost	503,736
Fair Value	518,929
State and Municipal Obligations [Member] \| Available-for-Sale securities, Maturity After 5 But within 10 Years [Member]
Amortized Cost	403,055
Fair Value	412,367
State and Municipal Obligations [Member] \| Available-for-Sale, Maturity After 10 Years [Member]
Amortized Cost	232,498
Fair Value	224,733
Mortgage and Asset-Backed Securities [Member] \| Agency Mortgage-Backed Securities [Member]
Amortized Cost	4,179,525
Fair Value	4,295,194
Mortgage and Asset-Backed Securities [Member] \| Non-Agency Mortgage-Backed Securities [Member]
Amortized Cost	351,629
Fair Value	353,229
Mortgage and Asset-Backed Securities [Member] \| Other Asset-Backed Securities [Member]
Amortized Cost	2,529,825
Fair Value	2,537,251
Other Debt Securities [Member]
Amortized Cost	160,083	165,883
Fair Value	167,633	176,964
Other Debt Securities [Member] \| Available-for-Sale Securities, Maturity within 1 Year [Member]
Amortized Cost	66,513
Fair Value	67,382
Other Debt Securities [Member] \| Available-for-Sale Securities, Maturity After 1 But within 5 Years [Member]
Amortized Cost	93,570
Fair Value	100,251
Equity Securities [Member]
Amortized Cost	14,905	7,569
Fair Value	40,723	39,173
Agency Mortgage-Backed Securities [Member]
Amortized Cost	4,179,525	2,437,123
Fair Value	4,295,194	2,491,199
Non-Agency Mortgage-Backed Securities [Member]
Amortized Cost	351,629	459,363
Fair Value	353,229	455,790
Total Mortgage and Asset-Backed Securities [Member]
Amortized Cost	7,060,979	5,239,352
Fair Value	$ 7,185,674	$ 5,301,249

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-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 FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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-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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-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 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-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 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-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 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

+ Details