Investment Securities, Available-for-Sale (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	3.07%	3.00%
Available for sale securities, Amortized Cost	$ 2,743,897	$ 2,394,978
Available for sale securities, Gross Unrealized Gains	48,823	24,182
Available for sale securities, Gross Unrealized Losses	(8,305)	(23,313)
Available for sale securities, Fair Value	2,784,415	2,395,847
Maturing within one year [Member] \| State and local governments and other issues [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	4.10%	4.06%
Available for sale securities, Amortized Cost	1,147	1,091
Available for sale securities, Gross Unrealized Gains	18	20
Available for sale securities, Gross Unrealized Losses	(3)	(5)
Available for sale securities, Fair Value	1,162	1,106
Maturing after one year through five years [Member] \| U.S. Government and federal agency [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	1.62%	1.62%
Available for sale securities, Amortized Cost	205	207
Available for sale securities, Gross Unrealized Gains	5	4
Available for sale securities, Gross Unrealized Losses	0	0
Available for sale securities, Fair Value	210	211
Maturing after one year through five years [Member] \| U.S. Government sponsored enterprises [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	2.31%	2.38%
Available for sale securities, Amortized Cost	35,245	40,715
Available for sale securities, Gross Unrealized Gains	793	715
Available for sale securities, Gross Unrealized Losses	0	0
Available for sale securities, Fair Value	36,038	41,430
Maturing after one year through five years [Member] \| State and local governments and other issues [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	2.44%	3.70%
Available for sale securities, Amortized Cost	100,685	8,341
Available for sale securities, Gross Unrealized Gains	1,205	214
Available for sale securities, Gross Unrealized Losses	(1)	(10)
Available for sale securities, Fair Value	101,889	8,545
Maturing after five years through ten years [Member] \| U.S. Government sponsored enterprises [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	1.89%	1.94%
Available for sale securities, Amortized Cost	83	84
Available for sale securities, Gross Unrealized Gains	0	0
Available for sale securities, Gross Unrealized Losses	0	0
Available for sale securities, Fair Value	83	84
Maturing after five years through ten years [Member] \| State and local governments and other issues [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	2.57%	3.73%
Available for sale securities, Amortized Cost	68,620	18,675
Available for sale securities, Gross Unrealized Gains	1,001	379
Available for sale securities, Gross Unrealized Losses	(7)	(56)
Available for sale securities, Fair Value	69,614	18,998
Maturing after ten years [Member] \| U.S. Government sponsored enterprises [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield		0.73%
Available for sale securities, Amortized Cost		4
Available for sale securities, Gross Unrealized Gains		0
Available for sale securities, Gross Unrealized Losses		0
Available for sale securities, Fair Value		4
Maturing after ten years [Member] \| State and local governments and other issues [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	4.88%	4.91%
Available for sale securities, Amortized Cost	794,825	639,364
Available for sale securities, Gross Unrealized Gains	23,731	5,281
Available for sale securities, Gross Unrealized Losses	(3,630)	(15,873)
Available for sale securities, Fair Value	814,926	628,772
Maturing after ten years [Member] \| Collateralized debt obligations [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	8.03%	8.03%
Available for sale securities, Amortized Cost	8,938	11,178
Available for sale securities, Gross Unrealized Gains	0	0
Available for sale securities, Gross Unrealized Losses	(2,985)	(4,583)
Available for sale securities, Fair Value	5,953	6,595
U.S. Government sponsored enterprises [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	2.31%	2.38%
Available for sale securities, Amortized Cost	35,328	40,803
Available for sale securities, Gross Unrealized Gains	793	715
Available for sale securities, Gross Unrealized Losses	0	0
Available for sale securities, Fair Value	36,121	41,518
State and local governments and other issues [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	4.46%	4.86%
Available for sale securities, Amortized Cost	965,277	667,471
Available for sale securities, Gross Unrealized Gains	25,955	5,894
Available for sale securities, Gross Unrealized Losses	(3,641)	(15,944)
Available for sale securities, Fair Value	987,591	657,421
Residential mortgage-backed securities [Member]
Comparison of amortized cost and estimated fair value of investment securities, available-for-sale
Available for sale securities, Weighted Yield	2.29%	2.23%
Available for sale securities, Amortized Cost	1,734,149	1,675,319
Available for sale securities, Gross Unrealized Gains	22,070	17,569
Available for sale securities, Gross Unrealized Losses	(1,679)	(2,786)
Available for sale securities, Fair Value	$ 1,754,540	$ 1,690,102

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
-Paragraph 15D
-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
-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 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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details